From the Guidelines
Laboratory testing for sun sensitivity should involve phototesting to determine the minimum erythema dose (MED) and consider screening plasma and erythrocyte porphyrin levels if cutaneous porphyria is a possibility, as recommended by the most recent study 1. When evaluating sun sensitivity, it is essential to consider the patient's medical history, including any previous reactions to sunlight or photosensitizing medications.
- Phototesting exposes small areas of skin to measured amounts of ultraviolet light to determine the MED, which is the smallest amount of UV radiation that causes redness.
- Screening plasma and erythrocyte porphyrin levels can help identify cutaneous porphyria, a condition that can cause skin damage following sun exposure.
- Genetic testing may be appropriate for hereditary photosensitivity disorders like porphyrias or xeroderma pigmentosum, as suggested by 1. Key considerations in laboratory testing for sun sensitivity include:
- The use of specialized equipment and expertise to properly interpret results and develop appropriate management strategies for specific photosensitivity.
- The potential for medication-induced photosensitivity, which may require temporarily discontinuing the medication if possible, as noted in 1.
- The importance of referral to a dermatologist if autoimmune skin disease is suspected, as recommended by 1. In terms of specific testing, the most recent study 1 suggests that plasma fluorescence scanning can be used as a first-line analysis for cutaneous porphyria, while fractionation of porphyrins in urine, faeces, and erythrocytes may be required to differentiate between different types of porphyria.
- The measurement of erythrocyte protoporphyrin with fractionation of metal-free and zinc-chelated protoporphyrin is essential to establish the diagnosis of acute painful photosensitivity symptoms caused by EPP or XLEPP, as noted in 1. Overall, laboratory testing for sun sensitivity should be guided by the most recent and highest-quality evidence, with a focus on determining the underlying cause of photosensitivity and developing effective management strategies to minimize morbidity, mortality, and improve quality of life.
From the Research
Lab Testing for Sun Sensitivity
- There are no direct studies on lab testing for sun sensitivity in the provided evidence.
- However, some studies mention sun sensitivity in relation to other topics, such as the use of doxycycline for acne treatment 2 and sun-protective behaviors among US adults 3.
- The study on doxycycline phototoxicity mentions that travelers to tropical countries taking doxycycline for malaria prophylaxis need thorough medical counseling to avoid possibly severe phototoxic reactions, which may be related to sun sensitivity 2.
- Another study found that disparities in sun-protective behaviors exist among different sexes, ages, education levels, and those reporting higher sun sensitivity, suggesting that sun sensitivity may be an important factor in determining sun-protective behaviors 3.
- A study on gene-sun exposure interactions in skin cancer found that sun exposure seems to interact with genes involved in pigmentation, oxidative stress, and immunosuppression, which may be related to sun sensitivity 4.