3 - Sunscreens Flashcards
Drug photosensitisation and photoinduced/photoaggravated dermatoses can be avoided or reduced with sunscreen use
True
UV radiation reaching the Earth’s surface can be divided into:
(1) UVB = 290-320 nm
(2) UVA = 320-400 nm
True
UVA can be further subdivided into:
(1) near UVA or UVA II = 320-340 nm
(2) far UVA or UVA I = 340-400 nm
The UVB blockers include:
(1) Octinoxate (octyl methoxycinnamate)
(2) Octisalate (octyl salicylate)
(3) Octocrylene
(4) Ensulizole (phenylbenzimidazole sulfonic acid)
True
The UVA blockers include:
(1) Oxybenzone (a type of benzophenone)
(2) Meradimate (methyl anthranilate)
(3) Avobenzone (butylmethoxydibenzoylmethane)
(4) Ecamzule (tetraphthalydine dicamphor sulfonic acid)
True
The physical blockers include:
(1) Titanium dioxide
(2) Zinc oxide
True
The Sun Protection Factor (SPF) is defined as the UV radiation required to produce 1 Minimal Erythema Dose (MED) on protected skin after application of 2mg/cm2 of sunscreen / the UV radiation to produce 1 MED on unprotected skin
True
Minimal erythema dose (MED) =
Broad spectrum sunscreen protection is defined as providing protection through the entire spectrum of both UVB and UVA wavelengths
True
UVB = 290-320 nm
UVA = 320-400 nm
Water resistant sunscreen products need to maintain the SPF level after 40 or 80 mins of water immersion
True
Sunscreens have traditionally been divided into:
(1) chemical absorbers
(2) physical blockers
based on their mechanism of action
True
Chemical sunscreens are generally aromatic compounds conjugated with a carbonyl group
True
Chemical sunscreens absorb high intensity UV rays, producing excitation to a high energy state; and upon return to ground state, the result is conversion of the absorbed UV energy into longer lower-energy wavelengths such as infrared radiation (heat)
True
Physical blockers reflect or scatter UV radiation, however microsized forms of physical blockers (also designated as inorganic particulates) also function in part by absorption
True
Para-aminobenzoic acid (PABA) was one of the first UVB chemical sunscreens to be widely available, though historically several problems limited the use of PABA
True
Several problems limited the use of Para-aminobenzoic acid (PABA) as it required an alcoholic vehicle
True (also stained clothing, associated with a subjective stinging and allergic contact dermatitis)
Several problems limited the use of Para-aminobenzoic acid (PABA) as it stained clothing
True (also required an alcoholic vehicle, caused subjective stinging and allergic contact dermatitis)
Several problems limited the use of Para-aminobenzoic acid (PABA) as it caused subjective stinging
True (also required an alcoholic vehicle, stained clothing and caused allergic contact dermatitis)
Several problems limited the use of Para-aminobenzoic acid (PABA) as it caused allergic contact dermatitis
True (also required an alcoholic vehicle, stained clothing and caused subjective stinging)
Padimate O (octyl dimethyl PABA) replaced the original para-aminobenzoic acid (PABA) as it had greater compatibility in a variety of cosmetic vehicles and had a lower potential for staining or other adverse reactions
True (UVB chemical sunscreen)
Despite being a potent UVB absorber, problems with PABA formulations in general have limited their use
True (both PABA and Padimate O, even though Padimate O is the most potent FDA approved UVB absorber)
Padimate O (octyl dimethyl PABA) is the most potent FDA approved UVB absorber
True (although the decline in PABA formulations due to allergic contact dermatitis, along with the demand for higher SPF products led to the incorporation of multiple active ingredients in a single product to achieve the desired SPF) - The cinnamates such as Octinoxate (octyl methoxycinnamate) largely replaced PABA derivatives such as Padimate O as the next most potent UVB absorber
The cinnamates such as Octinoxate (octyl methoxycinnamate) largely replaced PABA derivatives such as Padimate O as the next most potent UVB absorber
True
Octinoxate (octyl methoxycinnamate) is the most frequently used sunscreen ingredient
True (UVB absorber)
Octisalate (Octyl salicylate) is used to augment the UVB protection in a sunscreen as salicylates are weak UVB absorbers and are generally used in combination with other UV sunscreens
True
Octocrylene is a UVB absorber used in combination with other UV absorbers to achieve higher SPF formulations
True
Ensulizole (phenylbenzimidazole sulfonic acid) is a water soluble UVB absorber and is used in products formulated to feel lighter and less oily, such as in daily-use cosmetic moisturisers
True (most chemical sunscreen ingredients are oils soluble in the oil phase of emulsion systems which account for the heavy, greasy properties of many of these products)
Although benzophenones are primarily UVB absorbers, it’s derivative Oxybenzone also absorbs well through the near UVA/UVA II spectrum (320-340 nm), therefore benzophenones significantly augment the UVB protection of a sunscreen product while expanding into UVA coverage when used in a given formulation
True
Meradimate (methyl anthranilate) is a weak UVB filter that absorbs mainly in the near UVA II (320-340 nm) portion of the spectrum
True (it is a less effective sunscreen ingredient and is less widely used)
Avobenzone (butylmethoxydibenzoylmethane) provides superior protection through a large portion of the UVA spectrum including majority of the far UVA/UVA I spectrum (340-400 nm)
True (although photostability is a problem with Avobenzone, and it also has the potential to degrade other sunscreen ingredients in products such as the potent UVB cinnamate absorber octinoxate)
The photoinstability of Avobenzone can be offset by combining it with Octocrylene (used for photostability)
True
Octocrylene is a UVB absorber used in combination with other UV absorbers to achieve photostability
True (classically combined with the UVA absorber Avobenzone to offset Avobenzone’s photoinstability)
Ecamsule (tetraphthalydine dicamphor sulfonic acid) is a UVA filter with broad absorption profile from 290-390 nm (UVB 290-320 nm, near UVA 320-340 nm and far UVA 340-400 nm) with peak absorption at 345 nm (far UVA wavelength)
True
Poor cosmetic acceptance limited the widespread use of the physical blockers titanium dioxide and zinc oxide, until microsized forms became available
True
The physical blockers titanium dioxide and zinc oxide are inorganic particulate sunscreens which are reactive and poorly soluble and do not show significant skin penetration
True
The ideal sunscreen agent would be:
(1) chemically inert
(2) safe
(3) reflect through the full UV spectrum
True (the physical blockers titanium dioxide and zinc oxide)
By reducing the particle size of titanium dioxide to make it more aesthetically acceptable, titanium dioxide functions more by absorption and not simply by blocking (reflecting and scattering) UV radiation, therefore making titanium dioxide less effective in the UVA range than an opaque physical blocker
True (although this microsized ingredient can still be classified as a broad-spectrum agent)
Titanium dioxide causes a whitening effect on the skin secondary to pigment residue
True (the net effect might be that the user is inclined to apply the product less heavily, thus effectively lowering the SPF) - hybrid products using a combination of chemical UV absorbers with inorganic particulate blockers may represent a practical compromise
Zinc oxide is a physical blocker which offers the same advantages and disadvantages as titanium dioxide, although zinc oxide has more superior far UVA/UVA I protection (specifically 340-380 mm spectrum) than for titanium dioxide, thereby providing more full spectrum protection
True
Inorganic particulate microsized sunscreens are not effective in the short wavelength visible range and not suitable for patients with porphyria cutanea tarda or other porphyrias who require optimal photoprotection
True
Options for these patients include:
(1) protective clothing and sun avoidance (mainstay approach)
(2) opaque titanium dioxide or zinc oxide physical blockers
SPF 15 products block 93.3% of UVR (UVB) from penetrating the skin
True
SPF 15 = 93.3%
SPF 30 = 96.7%
SPF 50 = 98%
Theoretically an SPF 15 sunscreen product allows an individual to remain in the sun up to 15 times longer without burning, compared to what that individual’s intrinsic unprotected skin would allow
True (therefore a fair-complexioned individual who usually sunburns in 10 mins without any protection, would theoretically have >2.5 hours of protection from SPF 15)
Sunscreens are used for protection from UVR to prevent sunburn
True
Sunscreens are used for protection from UVR to prevent skin or lip damage, freckling and skin discolouration
True
Sunscreens are used for protection from UVR to prevent skin aging
True
Sunscreens are used for protection from UVR to prevent skin cancer
True
Sunscreens are used for protection from UVR to prevent phototoxic or photoallergic drug reactions
True
Sunscreens are used for protection from UVR to prevent photosensitivity diseases
True
Sunscreens are used for protection from UVR to prevent photoaggravated dermatoses
True
Sunscreen is contraindicated if there is known sensitivity to any active sunscreen ingredient
True
Sunscreen is contraindicated if there is known sensitivity to a vehicle ingredient in the product
True
Sunscreen is contraindicated in infants <6 months of age
True (sun avoidance is most appropriate for very young infants)
Sunscreen should not be used as the sole component of an overall program of photoprotection
True (a complete program includes protective clothing, shade and sun avoidance)
SPF 30 products block 96.7% of UVR (UVB) from penetrating the skin
True
SPF 15 = 93.3%
SPF 30 = 96.7%
SPF 50 = 98%
SPF 50 products block 98% of UVR (UVB) from penetrating the skin
True
SPF 15 = 93.3%
SPF 30 = 96.7%
SPF 50 = 98%
Product application technique alters SPF
True (in the laboratory, product thickness application is standardised as 2mg/cm2 whereas in the real world the thickness application is closer to 1mg/cm2)
SPF 30 sunscreen products provide significantly greater protection than that of the SPF 15 product with respect to sunburn cell production
True (even though the % UVR absorption between SPF 15 and SPF 30 is minute at 93.3% vs 96.7%)
The higher the SPF, the greater the near UVA /UVA II (320-340 nm) protection
True
Labelled SPF may overestimate the protection as temperate latitudes have a greater proportion of UVA than the solar-stimulated radiation prescribed by regulatory bodies
True
A broad spectrum sunscreen has a critical wavelength of >= 370 nm and generally these products will contain either Avobenzone (covers majority of far UVA/UVA I spectrum) or an inorganic particulate physical blocker as an active ingredient
True (the critical wavelength is determined to be the wavelength below which 90% of the total area of UV absorbance resides)
Sunscreen vehicles include:
(1) Emulsions - oil in water or water in oil
(2) Gels -water or alcohol based
(3) Sprays
(4) Sticks - thickened with waxes and petrolatum
(5) Cosmetics - foundation make up
True
The most commonly used sunscreens are lotions (oil in water emulsion) and creams (water in oil emulsion)
True
Newer ultrasheer sunscreen products use silica as a major vehicle component in the lotion/cream emulsion
True
Water based gel sunscreen products rely on limited number of water soluble active sunscreen ingredients such as Ensulizole or trolamine salicylate (both UVB absorbers)
True
Sunscreen gel products are easily removed by swimming and perspiration and tend to more readily cause facial or eye stinging
True (though may be favoured by individuals with oily skin or acne)
Spray sunscreen products are more convenient to apply but difficult to apply evenly and can produce a discontinuous film, resulting in a less effective sunscreen product
True
Sunscreen sticks are helpful for protecting the lips, nose or around the eyes
True
Foundation make up, even without sunscreen may provide some protection (SPF 4-5) because of its pigment content
True
By raising the level of pigments in foundation make up (including titanium dioxide), or by adding a chemical sunscreen, a higher SPF can be achieved
True
By virtue of the opacity of foundation make up, it provides the benefit of some UVA protection
True (functions as a physical blocker that reflects and scatters UVR)
The majority of sunscreen adverse reactions are irritant in nature
True
Subjective irritation including stinging, burning and itching without associated visible erythema is the most common adverse reaction to sunscreens
True (most frequently experienced in the eye area and stinging sensation can occur even if several hours have elapsed since sunscreen application)
An adverse reaction to sunscreen includes Erythema occurring immediately on contact with sunscreen that may represent contact urticaria which may be immunologic (IgE mediated type I allergy) or non-immunologic (due to toxic or direct mast cell degeneration part of the spectrum of subjective irritation)
True (sunscreens do not appear to be associated with an incidence of contact urticaria higher than that of other toiletries or cosmetics)
Sunscreens may cause irritant contact dermatitis
True
Sunscreens may cause allergic contact dermatitis (true type IV delayed hypersensitivity reactions)
True (though irritation is a more prevalent problem than true allergic contact dermatitis)
Virtually all sunscreen ingredients reported to cause allergy may also be photoallergens
True (although relatively uncommon, sunscreen active ingredients seem to have become the leading cause of photocontact allergic reactions)
Individuals with eczematous conditions have a significant predisposition to contact or photocontact dermatitis sensitisation because of impaired cutaneous barrier
True
Allergic or photoallergic contact dermatitis to sunscreen product should be considered in patients with a photosensitivity condition that suddenly changes or worsens as patients with photosensitivity dermatoses develop the majority of photocontact dermatitis to sunscreens
True (chronically photosensitive patients with eczematous changes who flare despite the use of broad spectrum sunscreen product may need patch testing or photopatch testing with a complete sunscreen series)
Sunscreen products may aggravate acne, though this is more related to the vehicle than to sunscreen ingredients
True (sunscreen vehicle ingredient may be comedogenic, but sunscreen oils are typically not)
Acne may also be aggravated by UV exposure (acne aestivale) and is not necessarily related to sunscreen product application
True
Sunscreen products may cause a form of irritation called contact folliculitis (rapid onset of small follicular papules and pustules shortly after product application), and gel or spray formulation may reduce the frequency of this adverse effect
True
UVA varies much less in intensity throughout the day (more constant intensity) than UVB
True
Sunscreens are most important from 10am to 4pm when the sun’s rays are strongest
True
For intermittent casual daily use, an SPF 15 sunscreen is sufficient
True
For prolonged recreational exposures, an SPF 30 sunscreen is more desirable especially for fair-skinned individuals
True
Sunscreens should be applied 15-30 mins before sun exposure to allow sufficient time of the protection to develop, and then reapplied every 2 hours
True
Individuals with polymorphic light eruption, taking photosensitising drugs, whose melasma or lentigines have darken despite sunscreen need better UVA protection through the entire spectrum including far UVA/UVA 1 (340-400 nm) and may benefit from products that contain Avobenzone, Ecamsule, titanium dioxide or zinc oxide
True
Subjective stinging in or near the eyes should not be interpreted as a sign of true allergy
True
Sunscreens with the chemically inert inorganic particulate materials such as titanium dioxide and zinc oxide as the only active ingredients provides a suitable alternative for patients with sensitive skin, regardless of what kind of sunscreen intolerance they have previously experienced
True
Individuals with oily complexions may prefer an oil-free alcohol-based gel or a lighter feeling cosmetic sunscreen moisturiser lotion
True (the oil-free claim refers to the vehicle as the active sunscreen ingredients themselves are oils)
The effects of sunscreen use on vitamin D levels in large-scale longitudinal studies are inconclusive
True (patients compliant with sunscreen use may get enough UVR through their sunscreen and non-covered areas to maintain adequate vitamin D levels)
For individuals practising vigorous photoprotection, daily intake of vitamin D though diet or supplements of 600IU would seem prudent (800IU for those >70 years old)
True (sunscreen application can inhibit vitamin D synthesis in studies in controlled settings, although large-scale longitudinal studies are inconclusive)
Sunless tanners (dihydroxyacetone is the active ingredient) has limited true sunscreen potential of SPF 3 or 4
True (gives a suntanned appearance, but is not sun-protective)
Dihydroxyacetone (DHA) in sunless tanners reacts with keratin and the epidermis to form melanoidins as a result of the Maillard or ‘browning reaction’ in the stratum corneum
True
The brown colour obtained on the skin from Dihydroxyacetone (DHA) in sunless tanners absorbed the low end of the visible spectrum with overlap into the far UVA spectrum, and so may provide some UVA I (340-400 nm) protection, although the SPF is only 3-4
True (only provides minimal sun protection, despite the tanned appearance)
Because the resultant brown colour from sunless tanners last up to several days, patients need to be reminded that the duration of UV protection (SPF 3-4) is more short-lived than that of the skin colour change
True
