Sunscreens have been associated with both allergic contact dermatitis and photo allergy.

With allergic contact dermatitis, a person typically develops an itchy skin rash only where the product is applied to the skin, and this is not unlike poison ivy, as the reaction may worsen over several days.

In contact photoallergy, the reaction is due to the combination of applied substance and sunlight; therefore skin symptoms appear only once the product-laden skin is exposed to the sun.

It can be rather difficult to distinguish the exact type of allergic reaction to sunscreen because sunscreens are applied to areas exposed to sunlight!

Sunscreen allergy (from both allergic contact dermatitis and photo-allergic reactions) can cause itching, blisters, red skin, and skin swelling.

People may have allergic skin reactions to chemical UV absorbers or even inactive ingredients in sunscreen, such as fragrances, formaldehyde releasers, preservatives, and lanolin. If a person develops allergic skin symptoms to sunscreen, patch testing can be performed.

Patch testing involves placing small patches or discs, each containing a separate chemical, on the skin for a period of time. This helps identify the cause of the reaction and can be done by an allergist or a dermatologist.

Options for people who have allergic skin reactions to sunscreens include protective clothing, and sunscreen formulations that contain ingredients that scatter or reflect (rather than absorb) UV radiation. Titanium dioxide and zinc oxide are in the family of "physical sunscreens" and are common UV blockers that have not been reported to cause allergic skin reactions such as contact dermatitis or photoallergy.