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Rheum/Musculoskeletal/Derm Week 3 > Sunscreen > Flashcards

Flashcards in Sunscreen Deck (10):

T or F. Profound systemic immunosuppression, such as in organ transplantation patients, can lead to an increased risk of skin cancer

T, as evidenced by the frequent development of nonmelanoma skin cancers in patients who have undergone organ transplantation, with reported incidence rates of 21% to 50%.



What are the categories of sunscreen?

chemical sunscreens and physical (inorganic). 

Each of the agents can also be categorized on the basis of the UV wavelengths that the product absorbs. UVB is 290-320 nm, UVA2 is 320-340 nm, and UVA1 is 340-400 nm.


Most organic UV filters (eg Cinoxate, Para-aminobenzoic acid (PABA) and Trolamine) absorb UV-B radiation, and a few (eg Dioxybenzone or Oxybenzone) also act in the UV-A2 range (320–340 nm).

Only one FDA-approved organic sunscreen, avobenzone, protects against UV-A1 (340–400 nm).


Inorganic compounds function by physically reflecting and scattering UV radiation from a film of inert metal particles, ie, in a manner similar to protective clothing.

What are the FDA approved inorganic sunscreens?

titanium dioxide and zinc oxide—provide UV-A and UV-B protection. Zinc oxide and the non-micronized form of titanium dioxide provide UV-A1 and UV-A2 protection. Inorganic sunscreens have a thick consistency and tend to clump. Advances in nanoparticle technology have improved their consistency, but micronized titanium dioxide does not provide UV-A1 protection.


What is SPF?

a laboratory measure of sunscreen efficacy and is defined as the amount of UVradiation required to produce a sunburn on protected skin relative to that of unprotected skin.  Since SPF assessment is based on erythema, it is mainly a measure of UV-B exposure, not UV-A exposure.


Contrary to popular belief, the SPF of a product is not related to the duration of UV exposure. Also, the relationship between SPF and UV-B protection is not linear: a sunscreen with an SPF of 15 can filter 94% of UV-B radiation, whereas an SPF of 30 provides greater than 97% protection at an equal UV-B dosage.

UV radiation dosage depends on both the duration of exposure and the intensity of the UV radiation. Thus, a sunscreen with twice the SPF does not necessarily mean one can stay out in the sun twice as long before developing a sunburn.


What is a broad-spectrum sunscreen?

Ability to block UV-A radiation: laboratory testing generates a curve of the absorbance within the UV spectrum. The area under this curve is calculated, and a “critical wavelength” is defined as the wavelength where the area under the absorbance curve up to that value is 90% of the total area under the curve. A sunscreen with “broadspectrum” UV-A protection is one for which the critical wavelength is greater than or equal to 370 nm. The critical wavelength measures the breadth of UV-A absorbance by a sunscreen and must be used in combination with the SPF value to provide a complete assessment of UV protection.


What is the Substantivity of a sunscreen?

a sunscreen’s ability to remain effective under adverse conditions such as exposure to water and sweat. A water-resistant product maintains the indicated protection after 40 minutes of water immersion, whereas a very-water-resistant (formerly called “waterproof”) product maintains the indicated protection after 80 minutes of water immersion.


What is sunscreen stability?

Important for long-lasting protection with continuous exposure to UV light, in particular to prevent photodegradation. The FDA has established maximum levels of each filter allowed in the sunscreen. Several filters can be combined to achieve a high SPF level, to provide broadspectrum UV-A and UV-B protection, and to prevent photodegradation.


New FDA sunscreen labeling mandates (2012)

The FDA’s SPF labeling requirements remained unchanged; however, the FDA instituted new regulations regarding UV-A protection. Sunscreens that qualify as broadspectrum are to be labeled as such, indicating that they protect against radiation in the entire UV spectrum.

Products that are “broadspectrum SPF ≥ 15” can now include the following statement in the “drug facts” part of the label: “If used as directed with other sun protection measures, decreases the risk of skin cancer and early skin aging caused by the sun.”

The FDA now requires sunscreens that are not broad-spectrum or that have an SPF less than 15 to include the following alert: “Spending time in the sun increases your risk of skin cancer and early skin aging.” These products can only claim protection from sunburn with the statement: “This product has been shown only to prevent sunburn, not skin cancer or early skin aging.”

In terms of water resistance, the FDA now bans the terms “sunblock,” “waterproof,” or “sweatproof,” as these claims cannot be substantiated. Instead, the label on the front of the package can only read either “water resistant (40 minutes)” or “water resistant (80 minutes).” Also, sunscreens may no longer claim to provide “instant protection,” nor can they claim to maintain efficacy for more than 2 hours without reapplication.

Some sunscreen products have been labeled with SPF values exceeding 100. The FDA decided that because there is insufficient evidence of clinical benefit for such SPFs, sunscreen product labels may claim a maximum SPF value of “50+.”