Diagnosis of Sun Allergy

Updated at: Jan 22, 2013
Diagnosis of Sun Allergy

Sun allergy is a common medical problem. To diagnose sun allergy, a doctor performs several tests such as UV light testing, photopatch testing, blood and sample tests.

Dr Poonam Sachdev
AllergyWritten by: Dr Poonam SachdevPublished at: Sep 06, 2012

Sun allergy or photosensitivity is an allergic reaction, which develops usually on the skin when exposed to ultraviolet rays of the sun. The severity of reaction may vary from mild to severe. Patients, who develop severe reactions from sunlight, need medical attention, however, most mild cases may be managed with self-treatment or avoidance of exposure to sunlight. Many other conditions, however, may cause symptoms similar to sun allergy. Hence, your doctor would like to ensure that your skin reaction isn't due to something other than a sun allergy. To diagnose the cause of your symptoms, the doctor will take a detailed history, examine you and if needed, do tests.

History and examination: Some questions that the doctor may ask are:

  • When did the symptoms start?
  • Have you had similar problem/s in the past?
  • Are the symptoms really bothersome and uncomfortable?
  • What seems to improve your symptoms or probably make it worse?
  • Have you been exposed to sunlight?
  • Are you on any long-term medications?

Discuss with your doctor all your medications. Some medicines that often cause phototoxic or photoallergic reaction on sunlight exposure includes thiazide diuretics, tetracycline antibiotics, NSAIDs (painkillers), etc. Your doctor may suggest medicines that are likely to cause this reaction.

Tests to diagnose sun allergy: Some tests that may be done to check skin reactions to sun exposure include:

  • UV light testing: This test is also known as phototesting. The test assesses the reaction of your skin to different wavelengths of ultraviolet light from a special type of lamp. It helps to determine the particular kind of UV light, which causes the reaction and can help pinpoint if your skin reaction is due to sunlight.
  • Photopatch testing: If the doctor suspects that some chemical (such as sunscreen or lotion) applied on your skin is causing your skin to react to sunlight, he will do photo testing. For the test, two identical patches of a substance, which is probably causing the reaction or allergy, are applied. After 24 hours, one site is exposed to UV light, but not the other. If a reaction occurs only on the exposed site, the particular chemical or skin product is confirmed to be responsible for allergy.
  • Blood tests and skin samples: Most people do not need these tests, but they may be done if he or she suspects some other cause (such as lupus) for your symptoms.


Read more articles on Sun Allergy Photosensitivity




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