If you have mild symptoms of PMLE, you may be able to diagnose the problem yourself by asking yourself the following questions:
Do I have an itchy rash that occurs only on sun-exposed skin?
Does my rash always begin within two hours of sun exposure?
Do my symptoms first appear during the early spring, and then gradually become less severe (or disappear) within the following few days or weeks?
If you can answer "yes" to all of these questions, then you may have mild PMLE.
If you have more severe sun-related symptoms — especially hives, blisters or small areas of bleeding under the skin — your doctor will need to make the diagnosis. In most cases, your doctor can confirm that you have PMLE or actinic prurigo based on your symptoms, your medical history, family history (especially American Indian ancestry) and a simple examination of your skin. Sometimes, additional tests may be necessary, including:
A skin biopsy, in which a small piece of skin is removed and examined in a laboratory
Blood tests to rule out systemic lupus erythematosus (SLE or lupus) or discoid systemic lupus erythematosus
Photo-testing, in which a small area of your skin is exposed to measured amounts of ultraviolet light — If your skin symptoms appear after this exposure, the test confirms that your skin eruption is sun-related.
If you have symptoms of a photoallergic eruption, the diagnosis may take some detective work. Your doctor will begin by reviewing your current medicines as well as any skin lotions, sunscreens or colognes you use. The doctor may suggest that you temporarily switch to an alternate medication or eliminate certain skin care products to see whether this makes your skin symptoms subside. If necessary, your doctor will refer you to a dermatologist, a doctor who specializes in skin disorders. The dermatologist may do photopatch testing, a diagnostic procedure that exposes a small area of your skin to a combination of both ultraviolet light and a small amount of test chemical, usually a medicine or ingredient in a skin care product.
If you have symptoms of solar urticaria, your doctor may confirm the diagnosis by using photo-testing to reproduce your hives.