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Rash

A diffuse rash on the back of a male
ICD-10	R21
ICD-9	782.1
MeSH	D005076

A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and therefore treatments for rashes, vary widely. Diagnosis must take into account such things as the appearance of the rash, other symptoms, what the patient may have been exposed to, occupation, and occurrence in family members. The diagnosis may confirm any number of conditions.

The presence of a rash may aid associated signs and symptoms are diagnostic of certain diseases. For example, the rash in measles is an erythematous, morbilliform, maculopapular rash that begins a few days after the fever starts. It classically starts at the head and spreads downwards.

Differential diagnosis[link]

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Common causes of rashes include:

• Food Allergy
• Anxiety.
• Allergies, for example to food, dyes, medicines, insect stings, metals such as zinc or nickel; such rashes are often called hives.
• Skin contact with an irritant
  • Fungal infection, such as ringworm
• Reaction to vaccination
• Skin diseases such as eczema or acne
• Exposure to sun (sunburn) or heat
• Friction due to chafing of the skin
• Irritation such as caused by abrasives impregnated in clothing rubbing the skin. The cloth itself may be abrasive enough for some people
• Menstruation
• Secondary syphilis

Uncommon causes:

• Autoimmune disorders such as psoriasis
• Lead poisoning
• Pregnancy
• Repeated scratching on a particular spot
• Lyme Disease
• Scarlet fever

Diagnostic approach[link]

The causes of a rash are extremely broad, which may make the evaluation of a rash extremely difficult. An accurate evaluation by a provider may only be made in the context of a thorough history (What medication is the patient taking? What is the patient's occupation? Where has the patient been?) and complete physical examination.

Points to note in the examination include:

• The appearance: e.g., purpuric (typical of vasculitis and meningococcal disease), fine and like sandpaper (typical of scarlet fever); circular lesions with a central depression are typical of molluscum contagiosum (and in the past, small pox); plaques with silver scales are typical of psoriasis.
• The distribution: e.g., the rash of scarlet fever becomes confluent and forms bright red lines in the skin creases of the neck, armpits and groins (Pastia's lines); the vesicles of chicken pox seem to follow the hollows of the body (they are more prominent along the depression of the spine on the back and in the hollows of both shoulder blades); very few rashes affect the palms of the hands and soles of the feet (secondary syphilis, rickettsia or spotted fevers,^[1] guttate psoriasis, hand, foot and mouth disease, keratoderma blenorrhagica);
• Symmetry: e.g., herpes zoster usually only affects one side of the body and does not cross the midline.

Overview of symptoms[link]

Treatment[link]

Treatment differs according to what rash a patient has been diagnosed with. Common rashes can be easily remedied using steroid topical creams (such as hydrocortisone) or non-steroidal treatments. Many of the medications are available over the counter in the United States.

See also[link]

• List of cutaneous conditions
• Dermatology

References[link]

External links[link]

Look up rash in Wiktionary, the free dictionary.

• Guide to rashes on Medline Plus Medical Encyclopedia - includes photographs
• Links to pictures of skin rashes (Hardin MD/Univ of Iowa)
• Various Rash Images from the US Medical Videos Journal