Skin Allergy: What the Rash Looks Like and When to Seek Help

Allergy is the immune system's reaction to a substance that does not harm most people. Normally the immune system protects against microbes, but in allergy it responds to a false alarm. Below — about skin manifestations: what the rash looks like, which other symptoms occur, what may be the cause, and when a doctor is needed.

What an allergic reaction on the skin is

Substances that trigger the reaction are called allergens. On the skin, allergy may manifest as a raised rash — it is called urticaria (hives). The skin may itch or redden, and redness is harder to notice on brown and black skin. Both genes and the environment probably play a role; people with allergy are often sensitive to several substances at once. Symptoms of an allergic reaction may appear within minutes or several hours later.

Which other symptoms occur

Besides the skin, allergy may affect breathing, the eyes, and digestion: there may be a runny nose and sneezing, red or watery eyes, cough, wheezing or shortness of breath, pain or tenderness in the area of the cheeks, eyes, and forehead, nausea, diarrhea, abdominal cramps, or bloating. Such signs relate to allergy in general, not only to the skin.

Swelling of the eyes, lips, mouth, or throat is a separate warning sign: it requires immediate help.

Causes of skin allergy

Common causes of allergy:

• tree and grass pollen, house dust mites, and mold spores;
• animal fur and dander, especially cats and dogs;
• foods such as peanuts, milk, and eggs;
• insect bites and certain medications.

Why the location of the rash does not determine the diagnosis

The expressions "allergy on the arm," "allergy on the legs," "allergy on the chest," or "allergy all over the body" describe the place where skin changes are noticeable, not a separate diagnosis. Skin manifestations of allergy are a raised rash (urticaria), itching, and redness of the skin.

Diagnosis and when to see a doctor

People see a doctor if they suspect an allergy in themselves or in their child. The doctor assesses the symptoms and may order testing: a skin test, in which a small amount of allergen is applied to the skin and the skin is checked for a reaction; blood tests; a special diet with a gradual increase in the amount of the suspected allergen. If necessary, the doctor will refer the patient to a specialized allergy clinic.

When emergency help is needed

A skin rash by itself is not a reason to call an ambulance; 103/112 — if the lips, tongue, mouth, or throat suddenly swell; breathing becomes faster or difficult, wheezing, a feeling of suffocation, or difficulty swallowing appears; the skin, tongue, or lips turn blue, gray, or pale; sudden confusion, drowsiness, dizziness, or fainting occurs; the child becomes lethargic and does not respond in the usual way. A rash that looks swollen, raised, or itchy may also be a sign of a serious allergic reaction (anaphylaxis). Anaphylaxis requires immediate treatment in a hospital.

This material is for reference: it describes the general signs of allergy and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer