SUNSCREENS

Skin damage from radiation is cumulative whether sunburn occurs or not.

Annual incidence: 500,000 cases of basal cell CA occur. 100,000 cases of squamous cell CA occur. 20,000 cases of malignant melanoma

occur.

ULTRAVIOLET RADIATION SPECTRUM

UVA (Longwave Radiation) Range 320-400 nm Erythrogenic activity is weak, however

penetrates dermis Responsible for development of slow natural

tan Most drug-induced photosensitivity rxn occurs UVA may augment the effects of UVB

UVB (Middlewave Radiation) Range 290-320 nm Erythrogenic activity is the highest Produces new pigment formation, sunburn,

Vit D synthesis Responsible for inducing skin cancer

ULTRAVIOLET RADIATION SPECTRUM

UVC (Shortwave or Germicidal Radiation) Range 100-290 nm. Does not reach the surface of the earth. Is emitted from artificial ultraviolet

sources.

ULTRAVIOLET RADIATION SPECTRUM

Long-term hazards of skin damage from radiation:

– Malignancy: • Squamous cell epithelioma• Actinic keratosis• Basal cell carcinoma

– Premature aging• nevus, seborrheic keratosis, solar lentigo• wrinkles, lines, etc

ULTRAVIOLET RADIATION SPECTRUM

SUNSCREEN CLASSIFICATIONS

Physical – Opaque formulations containing:

• titanium dioxide• talc, kaolin• zinc oxide• ferric chloride • icthyol, red petrolatum

– Mechanism: scatters or reflects UV radiation due to large particle size

Chemical– Formulations containing one or more:

• PABA, PABA esters• benzophenones• cinnamates• salicylates• digalloyl trioleate• anthranilates

– Mechanism: absorbs UV radiation

SUNSCREEN CLASSIFICATIONS

Sun Protection Factor (SPF) =

MED of Photoprotected Skin

MED of Unprotected Skin– MED is minimum dose of radiation which

produces erythema – SPFs are determined indoors using xenon

lamps which approximate the spectral quality of UV radiation

SUNSCREENS

SUNSCREENS

Factors which influence effectiveness of SPFs– Difference in skin types.– Thickness of the applied sunscreen.– Time of day.– Altitude: each 1,000 ft increase adds 4% to the intensity of

erythema producing UV radiation; thus intensity is about 20% greater in Pocatello than at sea level.

– Environment: snow/white surfaces reflect 70-90%, and when directly overhead water reflects nearly 100% of UVR.

– Vehicle: determines skin penetration of sunscreen.

SUNSCREENS

Category Skin Type SPF

I Always burns, never tans 15 >

II Burns easily 15

III Burns moderately, (avg caucasian) 10-15

IV Burns minimally, tans well (olive skin”) 6-10

V Rarely burns, tans profusely (brown skin) 4-6

VI Never burns (black skin) none

SUNCREEN AGENTSPABA (Para-aminobenzoic acid) Very effective in the UVB range (200-320 nm).

Most effective in conc of 5% in 70% ethanol. Maximum benefit when applied 60 min prior to exposure

(to ensure penetration and binding to stratum corneum).

Does NOT prevent drug/chemical-induced photosensitivity rxn.

Contact dermatitis can develop. May produce transient drying/stinging from alcohol

content (may be alleviated by adding 10-20% glycerol).

May stain clothing.

SUNCREEN AGENTS

PABA Esters (Padimate A, Padimate O, Glyceryl PABA)

Also very effective in UVB range (280-320) Most effective in conc. 2.5-8% in 65% alcohol May penetrate less effectively than PABA Similar application and adverse effect Less staining

Benzophenones (oxybenzone, dioxybenzone, sulisobensone)

Slightly less effective than PABA. Absorbs from 250-400 nm spectrum (ie, UVA & UVB). Combined with PABA or PABA ester improves

penetration and is superior to either agent used alone (200-400 nm wavelength coverage).

Beneficial in preventing photosensitivity rxns. Contact dermatitis is rare.

SUNCREEN AGENTS

SUNCREEN AGENTS

Cinnamates and Salicylates Minimally effective, absorb UVB spectrum. Generally used in combination with one of the

above.

SUNCREEN AGENTS

Anthranilates Minimally effective, absorbs UVA spectrum

250-322 nm. Usually combined with UVB agent to broaden

spectrum.

USE IN YOUNG CHILDREN

Not recommended in children < 6 mos (due to theoretical concern that percutaneous absorption may be greater and excretory functions may not be mature enough to handle).

No reported cases of toxicity. Recommend clothing (hats, etc).

Tan Accelerators– Contain tyrosine - necessary for production

of melanin, no evidence to support efficacy Sunless Tanners

– Dihydroxyacetone darkens outermost layer– Use at night, sunscreen during day

Tanning Booths– Newer types use light source composed of

95% UVA, < 5% UVB (even 1% may increase incidence of skin cancer).

TANNING

PHOTOSENSITIVITY REACTIONS

Photoallergic Reactions– Radiation alters drug, becomes antigenic or acts

as hapten.– Requires previous exposure.– Not dose related.– Induced by chemically related agents.– Eruption may present as urticarial, eczematous,

bullous, or sunburn-like reactions.– Usually caused by topical agents.

Phototoxic Reactions– Radiation alters drug to toxic form, causes

tissue damage.– Does not require previous exposure.– Dose related.– No cross-sensitivity.– Within several hours of exposure - appears

as exaggerated sunburn.

PHOTOSENSITIVITY REACTIONS

CHOOSING SPF RATING

HIGH SPF SUNSCREENS Can achieve higher SPF by combining

two or more agents. SPF 30 (3%) vs 15 (6%) of radiation

penetrating skin.

SUNSCREEN PRODUCTS

PABA/Ester Oxybenzone Other

Coppertone yes cinnamate

PreSun yes yes

Bull Frog yes cinnamate

Q.T. Quick Tanning cinnamate

Formula 405 Solar Lotion cinnamate

OTC BURN THERAPY

Burn Depth– First degree erythema, no

blistering– Second degree erythema and blisters– Third degree No blisters, leathery

white, mottled– Fourth degree “Charred”

CLASSIFICATION OF BURNS (American Burn Association)

Minor Burns: Second degree burn

Third degree burn

– excludes electrical or inhalation injuries and all poor risk patients.

< 15% BSA

(10% in children)

< 2% BSA not involving eyes, ears, face, hands, feet, or perineum).

Estimation of Burned Area

Rule of nines Body Area Head 9% Arm 9% Leg 18% Anterior Trunk 18% Posterior Trunk 18% Perineum 1%

OTC Treatment of Minor Burns/Sunburns

Ice/cool water Cleansing - water and nonirritating soap Dressings (usually only for second degree burns)

– Nonadherent primary layer of sterile fine-mesh gauze

– Absorbent intermediate layer to draw and store exudate

– Supportive outer layer of rolled gauze bandage

OTC Rx of Minor Burns/SunburnsLocal Anesthetics - short-term relief of pain Benzocaine 5-20% (eg, Americaine®) sensitivity rxn; no

systemic effects Lidocaine 0.5-4% (eg, Bactine®)

– Very low incidence of sensitivity rxn, but systemic toxicity may occur if applied to damaged skin or over large areas

Dibucaine 0.25-1% (eg, Nupercainal® Cream) Tetracaine 1-2% (eg, Pontocaine®) Pramoxine 1% (eg, Tronothane®) Topical Antibiotic (Bacitracin, Polymixin-B Oint.) Protectant (Sterile Petrolatum) - protects against

mechanical irritation and aids rehydration of stratum corneum. ASA for sunburns may help minimize inflammatory response.

POISON IVY/OAK/SUMAC Allergen:

– Urushiol is common to all of these plants– Transmission:

• Contact with resin causes sensitization; – may require as little as 1 mcg.

• Direct contact with plant is NOT necessary.– Plant must be injured/bruised to expose resin;

however requires very little friction to damage plant.

• Contact with resin may occur from shoes, family pet, firewood, etc

– weeks or months after initial exposure.

POISON IVY/OAK/SUMAC

Prevention:– Washing within 5-10 minutes may abort

reaction except in highly sensitive individuals.

– Resin penetrates skin rapidly and binds to skin proteins after which washing is useless

1 mcg may initiate rash in sensitive individual

POISON IVY/OAK/SUMAC

Symptoms:– Lesions are asymmetric and localized to

areas of contact– Itching, followed by erythema, edema,

papules (blisters)• (serum is not contagious)

– Onset usually within 24-48 hrs– Healing may take 2-3 weeks

POISON IVY/OAK/SUMAC

Treatment:– Weeping Lesions:

• Aluminum Acetate (Burow's Soaks) applied 15-30 min BID-QID and/or

• Aveeno bath (colloidal oatmeal) 2-3 times daily for 30 min

• po antihistamines for severe pruritus– AVOID topical: antihistamines, anesthetics, zirconium

– After lesions have dried:• Hydrocortisone CR 0.5% applied 4-6 times daily