Types of skin allergy

Skin allergy is not a single condition. Several types exist, and each has its own triggers, appearance and treatment.

Allergic contact dermatitis A delayed immune reaction to a substance touching the skin, such as nickel, hair dye, fragrance or rubber. The rash appears 1 to 3 days after contact and stays in the contact area.

Irritant contact dermatitis Not a true allergy. Harsh soaps, detergents, solvents or frequent wet work damage the skin directly. It is common in hands of homemakers, health workers and hairdressers.

Urticaria (hives) Itchy raised welts that last hours. Acute hives last under six weeks, often due to infection, food or medicine. Chronic hives last more than six weeks, and often have no clear cause.

Angioedema Deeper swelling of the lips, eyelids, tongue, hands or feet. It can occur with hives. Swelling of the throat or tongue is an emergency.

Atopic dermatitis (eczema) A long-term, relapsing, very itchy skin condition linked with allergy, asthma and hay fever, often starting in childhood.

Photoallergic and phototoxic reactions Rashes on sun-exposed skin after a medicine, plant or product combined with sunlight.

Drug eruptions Rashes triggered by medicines, ranging from mild itchy spots to rare severe reactions with blisters, fever and peeling, which need emergency care.

Food and insect allergy rashes Hives or flushing after eating a trigger food or an insect sting.