Rash
A skin change affecting color, texture, or appearance with varied causes.
A rash is a change of the skin that affects its color, appearance, or texture. Rashes may be localized or affect all the skin, causing symptoms such as itching, warmth, bumpiness, chapping, dryness, cracking, blistering, swelling, or pain. The causes and treatments for rashes vary widely, and diagnosis requires consideration of appearance, other symptoms, patient history, and family occurrence.
- field
- Dermatology
- common causes
- Food allergy, medication side effects, anxiety, skin contact with an irritant, fungal infection, balsam of Peru, skin diseases such as eczema or acne, exposure to sun or heat, friction, secondary syph
- uncommon causes
- Autoimmune disorders such as psoriasis, lead poisoning, pregnancy, repeated scratching, Lyme disease, scarlet fever, COVID-19
- diagnostic features
- Appearance, distribution, symmetry
- treatments
- Steroid topical creams (hydrocortisone, betamethasone) or non-steroidal treatments (salicylic acid, sulfur, tea tree oil, benzoic acid, zinc oxide, selenium sulfide, piroctone olamine, clotrimazole, m
Lore & Background
A rash is a change of the skin that affects its color, appearance, or texture. It 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.
Reader's Guide
The significance of a rash lies in its role as a diagnostic sign for various conditions. The presence of a rash may aid diagnosis; 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, classically starting at the head and spreading downwards. The evaluation of a rash is extremely difficult due to numerous causes, and an accurate evaluation requires a thorough history and physical examination. Points typically noted include appearance (e.g., purpuric, fine and sandpaper-like, circular lesions with central depression, plaques with silver scales), distribution (e.g., confluent with bright red lines in skin creases, vesicles following hollows of the body, rashes affecting palms and soles), and symmetry (e.g., herpes zoster usually only affects one side). Treatment differs according to the diagnosed rash; common rashes can be remedied using steroid topical creams or non-steroidal treatments, though steroid creams may be ineffective due to poor absorption except in mild cases.
Did You Know?
- A rash may be localized in one part of the body or affect all the skin.
- The rash in measles begins a few days after the fever starts and spreads from the head downwards.
- Herpes zoster usually only affects one side of the body and does not cross the midline.
- Steroid topical creams such as hydrocortisone may be ineffective due to inability to penetrate the skin through absorption.
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