A sun allergy, also known as photosensitivity, is diagnosed through phototesting. This involves a specific allergy test where patches of common sun allergy triggers are applied to your skin, usually on your back. A day later, one area receives a measured dose of UV rays from a sun lamp. A reaction only in the light-exposed area strongly suggests a link between the substance and the allergy.
Understanding Phototesting
Phototesting is the primary method for diagnosing sun allergies. This procedure is performed by dermatologists or allergists. It helps determine whether a reaction is caused by the sun itself or by a substance that interacts with sunlight.
- The Process: Patches containing potential allergens are applied to the skin. After a waiting period, one patch is exposed to UV light from a special lamp. The doctor observes the skin's reaction to identify which substances are causing the allergic response.
- UV Light Exposure: The UV light used is controlled to precisely measure the exposure, ensuring the test is both safe and effective. Different wavelengths of UV light can be used to pinpoint the specific type of light sensitivity.
- Reaction Analysis: Any reaction, such as redness, swelling, itching, or hives, only in the UV-exposed area points to a sun allergy related to the tested substance.
Other Diagnostic Methods
While phototesting is the most reliable method, your doctor may also use other methods:
- Patch testing: This helps identify substances that may trigger a reaction when combined with sunlight (phototoxic or photoallergic reactions).
- Physical Exam and Medical History: Your doctor will assess your symptoms, such as rash, hives, itching, and review your medical history to determine other possible causes.
Types of Sun Allergies and Related Tests
Various types of sun allergies exist, each requiring specific diagnostic approaches:
- Polymorphic Light Eruption (PLE): This common form often involves phototesting to determine sensitivity to specific UV wavelengths.
- Solar Urticaria: Characterized by immediate hives upon sun exposure. Phototesting confirms this diagnosis.
Remember that a proper diagnosis and treatment plan are best obtained from a dermatologist or allergist. They can perform the necessary tests and determine the best course of action based on your specific situation.
