Sunscreen and Sunblock

Cloud cover

70% to 90% of the UVR will penetrate.

Sunburn

is associated with UVR exposure as well as both drug and non-drug photosensitivity.

MED

is defined as the minimum UVR dose that produces clearly marginated erythema in the irradiated site, given a single exposure.

SPF

is derived by dividing the MED of protected skin by the MED of unprotected skin. SPF = 15 blocks 93% of the UVB SPF = 30 blocks 96.7% of the UVB SPF = 40 blocks 97.5% of the UVB NOTE: A SPF = 40 requires 25% more active agents than for a SPF = 30 product. Thus, to decrease possible systemic toxicities set maximum SPF = 30. NOTE: SPF is not a reliable measure of UVA protection

Wet Clothes

wet clothes allow the transmission of approximately 50% of UVR.

Dosing of sunscreens

• Face and neck: 1⁄2 tsp • Arms and shoulders: 1⁄2 tsp to each side of body • Torso: 1⁄2 tsp each to front and back • Legs and top of feet: 1 tsp to each side of body

UVB

(290-320nm) this is the most active UVR and produces erythema which is why it is called the sunburn radiation. Therapeutically it aids in Vitamin D synthesis. Nonetheless it is thought to be primarily responsible for causing skin cancer and contributes to causing premature aging of the skin.

UVA

(320 - 400 nm). Radiation penetrates deeper than UVB radiation (all the way into the dermis) resulting in vascular and histological damage. It is believed to cause premature aging of the skin, can trigger herpes simplex and photosensitive reactions. Can produce a tan without erythemia and is why it is used in tanning booths.

UVR

-effects are cumulative and can produce serious long term problems such as premature skin aging an skin cancer -avoiding excessive exposure will reduce the incidence of premature skin aging and skin cancer.

Mechanism of action of sunscreens

1.Sunscreen active ingredient: An active ingredient absorbs at least 85% of the radiation in 290 - 320 nm UV range but may or may not allow transmission of radiation to the skin at wavelengths longer than 320 nm. 2. Sunscreen opaque block:An opaque sunscreen active ingredient reflects or scatters all light in the UV and visible range from 290 to 777 nm.

Sensitive skin

Appropriate sunscreen+ moisturizer for dry skin

Child

Broad-spectrum sunscreen w/ SPF >30 for children greater than 6 months

Risk factors for development of UVR-induced problems

Fair skin that always burns, never tans, history of one or more serious or blistetring sunburns, blonde or red hair, blue, green or gray eyes, a history of freckling, a previous growth on the skin or lips caused by UV exposure, the existance of a uv-induces disorder, a family history of melenoma, current use of immunosuppresant drug, current use of photesensitizing drug, excessive lifetime exposure to UVR including tanning beds and booths, xeroderma pigmentosum

Tanning Booths

Have primarily UVA radiaiton, if properly used, can generate a tan without burning. However, there is a growing concern about the risk of skin cancer. Is associated with a significantly increased risk of both basal and squamous cell skin cancer. The risk is higher with use in early life (<25 years). This modifiable risk factor may account for hundreds of thousands of cases of non-melanoma skin cancer each year in the United States alone and many more worldwide. Because of the lower likelihood of erythema users become complacent and forgo the use of goggles. This practice will produce eye burns and may increase the risk of cataracts

SPF 30+

High sunburn protection

Aminobenzoic acids (PABA)

It can effectively block UVB radiation and has significant substantivity on sweating skin although not as much when submerged in water. The primary advantage of aminobenzoic acid derivatives over aminobenzoic acid is they do not stain clothing.

UVC

Little from the sun reaches the earth's surface and if it hits the skin it is absorbed in the upper most skin layer - the stratum corneum (composed of dead cells).

SPF 2-<12

Minimal sunburn protection

SPF 12-<30

Moderate sunburn protection

Previous allergic reaction to sun protectant

Physical sunscreen or sunscreen containing salicylate, cinnamate, methyl anthranilate or avobenzone

Water resistant

Product retains its SPF for at least 40 minutes.

Very Water Resistant

Product retains its sun protection for at least 80 minutes.

New FDA sunscreen rules

Sunscreens cannot be labeled as sunblock because such a claim is false. Only products with an SPF of 15 or higher can claim to reduce the risk of skin cancer and early sun aging. Sunscreens must protect equally against two kinds of the sun's radiation (UVB and UVA) to be labeled as offering broad spectrum protection. Products cannot be labeled waterproof or sweat proof. because such claims are false. They will be allowed to claim how long the product is water resistant. Dermatologists suggest that consumers look for products that are broad spectrum, have an SPF between 30-50 and should be reapply every 40 to 50 minutes

Suntan Products

Suntan Products: Those that contain a pigmenting agent and those that do not. Products that do not have a pigmenting agent are formulated with oily vehicles (e.g., mineral oil) and tend to concentrate UVR onto the skin. They provide no protection. The other type of suntan product contains the pigmenting agent dihydroxyacetone (DHA) and may or may not be formulated with an oily vehicle. DHA has been the major ingredient in the products that claim to tan without the sun. DHA does not provide provide protection against UVR. It colors the skin a reddish brown color by binding to specific amino acids in the stratum corneum. Color fads after 5 - 7 days due to the desquamation of the stratum corneum. It colors unevenly. Particularly dry areas such as the elbows and kneecaps will absorb more DHA.

Anthelios SX

The FDA has recently approved a new OTC for prevention of sunburn and for protection against UVB and UVA rays. It has a SPF of 15 and it contains ecamsule, avobenzone and octocrylene.

Substantivity

The ability to remain effective during prolonged exercising, sweating, and swimming

Sunscreen use in children

The absorptive characteristics of human skin in children younger than 6 months differ from those of adult skin. Also, metabolic and excretory systems in infants are not fully developed to handle any sunscreen absorbed through the skin. Thus, the FDA requires the statement: "children under 6 months of age: ask a doctor."

Benzophenones

These agents are primarily UVB absorbers but also extends into the UVA region. Thus, many products contain these agents due to their broader spectrum and because some patients may be allergic to the aminibenzoic acid derivatives.

Germicidal radiation

UVC radiation (200-290nm)

Oral Pigmenting Agents

Unproven Suntan Agent: Their active ingredients are the dyes canthaxanthin and b-carotene. Both are approved by the FDA as color additives in foods. But the concentrations used in foods are 1/20th to 1/40th of that found in the oral products claiming to produce a tan. The dyes alter skin tone by coloring fat cells under the epidermal layer. The extent of tan varies from person to person. One major concern with these additives is the discoloration of the feces to brick red, which could mask GI bleeding

Tan Accelorators

Unproven suntan agent: These are cosmetic products that claim to stimulate a faster and deeper tan. They consist of tyrosine, an amino acid necessary to produce melanin. There is no current evidence to support that these products work.

Melanotropins and Melanin Products

Unproven suntan agent: a-Melanotropin (a-MSH i.e., a- melanocyte-stimulating hormone) is currently under investigation to see if it can effect tanning - its effectiveness is yet to be demonstrated. Melanin products have also not yet been shown to be effective.

drug and non-drug photosensitivity causes

Visible, UVA (long wavelength UV) and UVB (medium wavelength UV) but UVB is most problematic.

Physical sunscreens

Zinc oxide or titanium dioxide. Note: manufactures have developed a way to make titanium dioxide transparent. As such, it is being combined with other sunscreen agents to increase the spectrum of UVR protection. Problem with zinc oxide and titanium oxide is that they discolor clothing and may occlude the skin to produce miliaria (prickly heat) and folliculities.

UVA

penetrates window glass. So even with the windows up in a car patients who are sensitive to UVA will be affected.

Fresh Snow

reflect 85% - 100% of the light and radiation that strikes it.

Water

reflects no more than 5% of UVR allowing the remaining 95% to penetrate and burn the swimmer.