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Papular urticaria | Parapsoriasis | Paronychia | Pediculosis | Peels (see chemical peels) | Pemphigoid (go to pemphigus and bullous pemphigoid) | Pemphigus and bullous pemphigoid | Perioral dermatitis | Peutz Jeghers syndrome | Photosensitivity | Pigmentation (go to melasma) | Pigmented purpuric dermatosis | Pimples (go to acne vulgaris) | Pitted keratolysis | Pityriasis alba | Pityriasis lichenoides | Pityriasis rosea | Pityriasis rubra pilaris | Pityriasis versicolor or tinea versicolor | Poikiloderma of Civatte | Polymorphic light eruption | Pompholyx | Porokeratosis | Porphyria cutanea tarda | Portwine stain | Pregnancy rashes | Prickly heat (go to milaria) | Prurigo nodularis | Pruritus | Pruritus ani | Pruritus vulvae | Pseudofolliculitis barbae (razor bumps) | Psoriasis | Purpura | Pyoderma gangrenosum | Pyogenic granuloma

PAPULAR URTICARIA

Papular urticaria is a condition that usually affects the legs and other exposed parts such as the arms and face. It may affect any age group but is more common in children.

    Cause

  • Insect bites eg., fleas and mites from infested cats, dogs and birds.
  • Reaction to insects or their products such as eggs and faeces.

    Symptoms

  • Crops of itchy papules (bumps) and sometimes, blisters.
  • Scratching leads to crusting and open sores.
  • New spots may reactivate old ones.

    Complications

  • Infection due to scratching.

    What you can do

  • You should a doctor.
  • Keep the house clean and insect free.
  • Keep pets outside.
  • Keep pet houses clean and pest free.
  • Use insect repellents.
  • Try to be as fully clothed as possible.
  • Take antihistamines for itching.

    What the doctor may do

  • Try to determine the cause (which may not always be possible).
  • Treat with topical steroids or intralesional steroids.
  • Treat infection with antibiotics.
  • Prescribe antihistamines for itching.

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PARAPSORIASIS

This consists of a group of disorders that produce a persistent red scaly rash that look a little like psoriasis (hence, the name, "parapsoriasis". Some forms are harmless but parapsoriasis en plaques is serious because it may progress to mycosis fungoides, a cutaneous (skin) lymphoma.

    Symptoms

  • Yellow-red to brown slightly raised patches with a fine scale.
  • Usually occurs on the trunk, thighs and buttocks.
  • May itch.

    Complications

  • Many develop into mycosis fungoides.

    What you can do

  • You should consult a doctor.

    What the doctor may do

  • Perform a skin biopsy to confirm the diagnosis.
  • Treat with topical steroids, UV-B phototherapy or PUVA.
  • Follow up closely for development of mycosis fungoides.

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PARONYCHIA

Paronychia is an inflammation of the nailfolds. It may be acute or chronic.

    Causes

  • Acute paronychia is caused by a bacteria, usually the staphylococcal or streptococcal bacteria and occasionally, the pseudomonas and proteus bacteria.
  • Chronic paronychia may be caused by:
     
     
    Aggravating factors
  • Frequent immersion in water eg., in fishmongers, housewives, bartenders, and domestic maids.
  • Trauma such as pushing and clipping the cuticles.
  • Hangnails.
  • Poor circulation.

    Symptoms

  • Acute paronychia - severe throbbing pain, collection of pus or pus discharging from under the nailfolds.
  • Chronic paronychia - red, tender swelling around the nails with discoloured, roughened nails.
      Acute paronychia.
    Click on image for larger view
    What you can do
  • You should consult a doctor.
  • Paronychia cannot be cured until a new cuticle forms to seal off the gap between the nailfold and the nailplate. Careful nailcare and long-term measures are necessary.
  • Keep the hands clean and dry. Avoid frequent handwashing and wear protective gloves for wet chores (see hand eczema).
  • Keep the nailfolds clean. Apply spirit lotion or some other antiseptic to prevent acute infections.

    What the doctor may do

  • Incise and drain the collection of pus in acute paronychia.
  • Prescribe oral antibiotics for acute paronychia.
  • Prescribe oral antifungals in cases of candidal paronychia.
  • Counsel about proper hand care.

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PEDICULOSIS

Pediculosis is the medical term for louse infestation of the skin. The louse (singular for lice) lives by biting and feeding on the blood it extracts and can infest any part of the body that has hair. Three types of lice infestation may be seen:

  • Pediculosis capitis (head lice) which affects the scalp and occasionally, the eyebrows and eyelashes.
  • Pediculosis corporis (body lice) which affects the body.
  • Pediculosis pubis (pubic lice) which affects the pubic region primarily and the lower abdomen, eyebrows, eyelashes and armpits occasionally.
     
    Causes
  • Pediculosis capitis, caused by the head louse can be transmitted by:
    • Sharing combs, brushes (especially by schoolgirls), hats and towels.
    • Head-to-head contact.
     
  • Pediculosis corporis, caused by the body louse can be transmitted by:
    • Sharing clothing or other personal items.
     
  • Pediculosis pubis, caused by the pubic louse (crab louse) can be transmitted by:
    • Sharing beds, clothing or towels.
    • Close physical contact, eg., during sexual intercourse.


    Symptoms

  • Pediculosis capitis
     
    • Itchy scalp.
    • Presence of the lice themselves.
    • Nits (eggs) attached to the hair. Although nits can resemble dandruff, they cannot be flicked off or moved along the hair with the fingers. They may sometimes be found on the eyebrows, eyelashes and beard, as well.
    • Groups of red itchy papules (pimply bumps) on the neck.
     
  • Pediculosis corporis
    • Generalised itching.
    • Red papules (pimply bumps) and bloody crusts at the points where the clothes comes into closest contact with the skin, eg., beneath collars, under the belt, under underwear and in the armpits.
    • Scratch marks, particularly in between the shoulder blades.
    • Pigmentation of the skin may be seen in longstanding cases.
    • Lice and nits are usually found in the clothes, only rarely are they found on the body hairs.
     
  • Pediculosis pubis
    • Affects the lower abdomen, upper inner thighs and occasionally also the armpits, eyebrows, eyelashes and hairline.
    • Pubic itch.
    • Red itchy papules (pimply bumps).
    • Scratch marks.
    • Lice themselves.
    • Dried specks of blood on the underwear.
    • Nits attached to the pubic hair and occasionally, the eyebrows, eyelashes, armpit hair and hairline of the scalp.
    • Blue pigmentation may be present over the lower part of the abdomen, upper inner thigh and the armpits in chronic cases.

      Pediculosis pubis.
    Click on image for larger view

    Complications

  • Secondary bacterial infection.

    What you can do

  • You should consult a doctor to confirm the diagnosis.
  • Follow the doctor's instructions on treatment. Do not overuse anti-lice medicines as some of them are irritating to the skin and can be toxic.
  • Take antihistamines to relieve itching.

    What the doctor may do

  • Look for nits or the lice themselves. In pediculosis corporis, the nits and lice are found in the seams of clothings rather than on the skin.
  • Prescribe anti-lice applications such as permethrin, benzyl benzoate, gamma benzene hexachloride, pyrethrin with piperonyl butoxide and crotamiton.
  • Prescribe antibiotics for secondary infection.

    Keypoints
  • Family members require treatment, as well. Sex partners of individuals with pediculosis pubis (pubic lice) also need treatment. Classmates of those with pediculosis capitis (head lice) need to be examined.
  • In pediculosis corporis (body lice), the nits and lice are found in the seams of clothings. Clothing must washed in hot water or dry cleaned and the seams must be ironed.
  • Nits can remain on the hair after successful treatment. These can be removed by soaking the hair with 1:1 vinegar:water solution for 30 minutes under a shower cap or towel and then combing through with a fine toothed comb.

    Prevention

  • Avoid close contact with infested persons.
  • Avoid sharing hats, combs, towels and other personal items.
  • Bathe and change clothes frequently.
  • Avoid casual sex.

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PEMPHIGUS AND BULLOUS PEMPHIGOID

These are skin diseases that cause the skin to blister.

    Cause

  • Autoimmune (self-allergy) disease in which antibodies are produced against the intercellular cement which hold the epidermal cells together (pemphigus) or the basement membrane which anchors the epidermis to the dermis beneath (bullous pemphigoid).
  • Inherited as in Hailey-Hailey disease (familial benign chronic pemphigus).

    Symptoms

  • Pemphigus
     
    • Multiple flaccid blisters that rupture easily, leaving raw painful areas.
    • Ulcers in the mouth.
    • Usually affects the middle-aged and elderly.
     
    There are several types of pemphigus for example pemphigus foliaceus, pemphigus vegetans, pemphigus vulgaris, pemphigus erythematosus and Hailey-Hailey disease (familial benign chronic pemphigus).
     
  • Bullous pemphigoid
     
    • Itchy red patches which later develop into tense, fluid-filled blisters.
    • The blisters may also develop on normal skin.
    • The mouth is usually not affected.
    • Bullous pemphgoid usually affects the elderly.
      Bullous pemphigoid.
    Click on image for larger view
    Complications
  • More common with pemphigus.
  • Secondary bacterial infection which may lead to septicaemia (blood poisoning) and fatality.
  • Fluid and electrolyte imbalance due to loss through the exposed raw skin.

    What you can do

  • You should consult a doctor.

    What the doctor may do

  • Admit for management.
  • Prescribe oral steroids with or without immunosuppressive drugs.
  • Prescribe antibiotics for secondary infection.

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PERIORAL DERMATITIS

This condition more commonly affects in women in the 20s and 30s and may be mistaken for acne vulgaris.

    Causes

    The most common cause is the inappropriate use of strong topical steroids on the face. Other factors that may play a role include:
     
  • Atopic tendency.
  • Inadequate cleansing.
  • Overuse of moisturisers, foundation and sunscreens.
  • Acne rosacea.
  • Candidiasis.
  • Fluoride toothpastes.
  • Sun-exposure.
     
    Symptoms
  • Small red papules (bumps) on a red scaly base.
  • Occurs around the mouth sparing a strip of skin near the lips.
  • Occasionally, the skin around the nose and eyes are also affected.
  • Itching or occasionally, a burning sensation can be felt.
      Perioral dermatitis.
    Click on image for larger view
    What you can do
  • You should consult a doctor.
  • Cleanse with mild soaps.

    What the doctor may do

  • Wean off or stop strong topical steroids (this is often followed by a temporary flare-up).
  • Prescribe oral antibiotics for 2 - 3 months.

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PEUTZ JEGHERS SYNDROME

This is an inherited disorder that causes freckles on the lips and gums and polyps in the gastrointestinal tract.

    Cause

  • Inherited in an autosomal dominant fashion which means the offspring has a 1 in 2 chance of inheriting the disease from an affected parent.

    Symptoms

  • Appears in early childhood.
  • Blue-brown or brown freckles on the lips and mouth.
  • Multiple polyps in the gastrointestinal tract, especially in the small intestine where they may cause abdominal pain, vomiting and haemorrhage.

    Complications

  • There is a 2% risk of cancer developing in the polyp.

    What you can do

  • You should consult a doctor.

    What the doctor may do

  • Perform tests to exclude intestinal polyps.
  • Follow up closely for the development of cancer.
  • Us a pigment laser to remove the freckles for cosmetic reasons.

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PHOTOSENSITIVITY

Photosensitivity refers to an abnormal sensitivity to sunlight. Sensitivity may occur to ultraviolet B (short wave ultraviolet light that causes sunburn), ultraviolet A (long wave ultraviolet light that causes tanning) or even to visible light. Sometimes the sensitivity is so severe that even artificial light sources such as fluorescent lamps can cause it. Photocontact dermatitis is a type of allergic contact dermatitis which only occurs in the presence of light.

Drugs causing photosensitivity Action
Amiodarone Heart medicine
Chlorpropamide Antidiabetic medicine
Frusemide, thiazides Diuretics (used to remove excess water from the body)
Griseofulvin Antifungal medicine
Tetracycline, sulphonamides, nalidixic acid Antibiotics
Phenothiazines Antihistamine, tranquilliser
Psoralens Photosensitising medicine used in PUVA
Tretinoin and isotretinoin Vitamin A acids (retinoids) used in the treatment of acne

    Skin conditions aggravated by sunlight

  • Lupus erythematosus
  • Acne rosacea
  • Herpes simplex virus infections
  • Darier's disease. (a rare inherited skin disorder)
  • Porphyria (rare metabolic disorder)

    Symptoms

  • Rash on the sun-exposed areas sparing the shaded areas around the eyes, behind the ears and under the chin.
  • Streaky pigmentation on the sides of the neck from perfumes and on the forearms from phytophotodermatitis (plant induced contact dermatitis).

    What you can do

  • You should consult a doctor.
  • Protect yourself against the sun (see sun protection).

    Sun-protection

  • Limit exposure to sunlight especially between 11am to 3pm.
  • Wear protective clothing (densely woven fabric is best) and brimmed hats, and use umbrellas.
  • Use sunscreens.
  • Remember that the sun can penetrate through water and wet white clothing and UV-A can pass through window glass. You may need to use special solar films on windows in the car and at home. Enquire from your doctor.

    What the doctor may do

  • Determine the cause with the help of photo- and photo-patch tests (special light tests).
  • Eliminate or treat the underlying cause.
  • Counsel about sun protection.

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PIGMENTED PURPURIC DERMATOSIS

This refers to a group of disorders characterised by reddish-brown spots or patches. They are caused by the leakage of blood through the tiny capillaries the skin. Hence, it is also called capillaritis. The red colour is due to the blood pigment, haemosiderin. Exactly why the capillaries should become leaky is not known for certain but a hypersensitivity reaction to viral infection, food additives and medications have been cited. Types of pigmented purpuric dermatosis include:

  • Gougerot-Blum syndrome (pigmented purpuric lichenoid dermatosis)
    • Itchy red brown spots and bumps that join together to form a thickened patch.
     
  • Schamberg's disease (progressive pigmented purpura)
    • Flat red brown patches with rust coloured spots that look like cayenne pepper on the ouside.
    • Not itchy.
     
  • Majocchi's disease (purpura annularis telangiectoides)
    • Like Schamberg's disease but with telangiectasias (dilated capillaries) and arranged in rings.
     
  • Itching Purpura
    • Like Schamberg's but is more widespread and itchy.
     
  • Lichen aureus
    • Patch has a yellowish hue (hence the term aureus means golden).
    • Usually occurs over varicose veins.


    Key point

  • A similar rash has been reported due to an allergy to some dyes used in khaki uniforms.

      Pigmented purpuric dermatosis.
    Click on image for larger view

    What you can do

  • You should consult a doctor.
  • Wearing compression stockings can help.

    Treatment

  • Reassure the patient that it is mainly a cosmetic problem.
  • Identify and remove the cause, if any.
  • Prescribe topical steroids which may occasionally help.

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PITTED KERATOLYSIS

This is a relatively common bacterial skin infection affecting the feet in people with sweaty feet or who wear heavy shoes a lot. It usually affects adolescents and young adults.

    Causes

  • Infection by a bacteria such as Corynebacterium minutissimum and Dermophilus congolensis.
  • Infection is encouraged by moisture and warmth so pitted keratolysis usually affects the feet of people who wear heavy shoes and people with hyperhidrosis (sweaty feet).

    Symptoms

  • Irregular white patches with pits. The appearance is most dramatic when the feet is wet.
  • Pitted keratolysis usually affects the pressure areas of the feet such as the forefeet, heels and toe pads.
  • Hyperhidrosis (sweaty feet) may be present.
  • The feet may smell.

      Pitted keratolysis.
    Click on image for larger view

    What you can do

  • You can consult a doctor.
  • Wear full leather shoes (ie., leather uppers and soles) which allow the skin to "breathe" or wear open footwear, whenever possible.
  • Wear heavy shoes for short periods at a time.
  • Switch to cotton socks.
  • Change socks frequently and alternate between two pairs of shoes, allowing one to dry completely before wearing.
  • Replace old smelly shoes.
  • Wash with soap or antiseptic cleanser twice a day.
  • Use antiperspirants to reduce sweating.
  • Sprinkle dusting powder or corn starch to absorb the sweat.

    What the doctor may do

  • Prescribe oral antibiotics, topical antibiotics or Castellani paint.
  • Treat associated hyperhidrosis.

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PITYRIASIS ALBA

Pityriasis alba causes pink slightly scaly patches which clear, leaving patches of paler looking skin. The pink stage is mild and often go unnoticed. Most patients are alerted by the pale patches. Pityriasis alba usually affects young children and occasionally, young adults, as well. It is more noticeable in darker skinned individuals, especially after a spell in the sun. Pityriasis alba may affect the face, neck, upper trunk and upper portions of the limbs.

    Causes

  • May be a mild form of atopic dermatitis or xerosis (skin dryness).
  • The affected areas are less able to tan compared to the surrounding skin.

    Symptoms

  • Pink, slightly scaly patches initially. This stage often passes unnoticed.
  • Pale patches appear after the pink patches clear. This is the stage that most patients notice and seek medical attention because of concerns about pityriasis versicolor, a fungal infection that causes pale patches.
  • The pale patches become more obvious after exposure to the sun because the affected areas tan poorly compared to the surrounding skin.
  • Non-itchy.
  • Pityriasis alba usually clears after several months to years even without treatment.
      Pityriasis alba.
    Click on image for larger view
    What you can do
  • You should consult a doctor to confirm the diagnosis.
  • Use mild soaps.
  • Apply moisturisers.
  • Use sunscreens to prevent the surrounding skin from darkening and accentuating the pale patches.

    What the doctor may do

  • Exclude other conditions that cause pale patches such as leprosy, pityriasis versicolor and vitiligo.
  • Prescribe mild topical steroids.

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PITYRIASIS LICHENOIDES

Pityriasis lichenoides is an uncommon skin disorder that affects adolescents and young adults. It occurs in two forms:-

  • Pityriasis lichenoides acuta et varioliformis (PLEVA) or Mucha Haberman disease.
  • Pityriasis lichenoides chronica (PLC).

    Cause

  • The cause is unknown but it is generally believed to be a hypersensitivity reaction to an as yet unidentified microorganism.

    Symptoms

  • Pityriasis lichenoides acuta et varioliformis (PLEVA) or Mucha Haberman disease
     
    • Crops of red papules (bumps) which blister and crust over and heal, leaving depressed scars rather like chickenpox.
    • New crops appear as old ones heal.
    • PLEVA usually affects the trunk and the insides of the forearms and back of the legs.
    • The person usually feels well, although occasionally, there may be a slight fever or headache.
    • PLEVA tends to be very persistent.
     
  • Pityriasis lichenoides chronica (PLC)
     
    • PLC causes small red brown spots with an adherent scale that can be scraped off to reveal a shiny brown surface. These scales are often referred to as mica scales.
    • PLC usually affects the trunk and the insides of the thighs and forearms.
    • The rashes take a long time to clear, hence the name "chronica" and often leaves a brown stain that may take months to fade.

      Pityriasis lichenoides.
    Click on image for larger view

    What you can do

  • You should consult a doctor.
  • Moderate exposure to the sun without getting burnt may help to clear pityriasis lichenoides chronica.

    What the doctor may do

  • Perform a skin biopsy to confirm the diagnosis.
  • The doctor may prescribe topical steroids, antibiotics for 2 - 3 months or use phototherapy. Pityriasis lichenoides is not, generally, very responsive to treatment.
  • If PLEVA is very persistent, he may even prescribe methotrexate, an immunosuppressive drug.

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PITYRIASIS ROSEA

This is a relatively common, self-limiting skin disorder that affects mainly children and young adults.

    Causes

  • May be due an to infective agent such as a virus.
  • Secondary syphilis and drugs such as barbiturates (a tranquilliser), metronidazole (an antibiotic), gold (sometimes used for treating rheumatoid arthritis), captopril (used for treating severe high blood pressure), clonidine (used for treating high blood pressure) and penicillamine (sometimes used for treating rheumatoid arthritis) have been reported to cause a pityriasis rosea-like rash.

    Symptoms

  • Starts as a single 2 - 5 cm pink or brown patch with a fine scaly border on the trunk, upper arms, neck and thigh. This patch is called the herald patch because it is followed by a more generalised rash.
  • The generalised rash appears 5 - 10 days later on the trunk and upper portions of the limbs. It is comprised of multiple pink, oval shaped patches measuring 0.2 - 2 cm in diameter. The surface has a wrinkled appearance and a fine "cigarette-paper" white scale (known as a colarette) can be seen around the border. On the trunk, the long axes of the rash run parallel to the ribs, resulting in a "Christmas tree" pattern.
  • Itching is usually absent, although in a few individuals, it can be unusually severe.

      Pityriasis rosea.
    Click on image for larger view

    What you can do

  • You should consult a doctor.
  • Although a viral cause is suspected, isolation is not necessary.
  • Mild exposure to sunlight may help the problem clear faster.
  • Take antihistamines if itching is severe.

    What the doctor may do

  • Exclude other causes.
  • Prescribe topical steroids.
  • Use UV-B phototherapy using to clear persistent cases.

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PITYRIASIS RUBRA PILARIS

This is a rare disorder of keratinisation, the process by which cells accumulate keratin as they reach the surface of the skin.

    Cause

  • Inherited - Inhe