The primary use of sunscreens is to protect the skin from the short-term and long-term effects of ultraviolet radiation. In today’s scenario of procedure-centered dermatology, sunscreens have become an indispensable part of every patient’s post-procedure skincare routine. The common indications for the use of sunscreens in dermatology care in the prevention and management of:
- Freckling, discoloration
- Skin cancer
- Phototoxic/ photoallergic reactions
- Photosensitivity diseases
- Polymorphous light eruption (290-365 nm)
- Solar urticaria (290-515 nm)
- Chronic actinic dermatitis (290 nm-visible)
- Persistent light reaction (290-400 nm)
- Lupus erythematosus (290-330 nm)
- Xeroderma pigmentosum (290-340 nm)
- Photoaggravated dermatoses
- Post-inflammatory hyperpigmentation (post-procedure)
Spectrum of UV radiation
The biologically active components of ultraviolet (UV) radiation include UVA and UVB radiation. The primary targets of UV radiation in the skin are:
UVB (290-320 nm)
- Responsible for the most severe damage
- Direct impact on cell DNA and proteins
- Acute damage – sunburn
- Long-term damage – cancer
UVA (320-400 nm)
- Not directly absorbed by biological targets
- Penetrates deeper than UVB
- Affects connective tissue by producing reactive oxygen species; produces profound immunosuppression
- Responsible for tanning, photoaging, photocarcinogenesis, exogenous photosensitization and many idiopathic photodermatoses (including polymorphous light eruption)
Classification of Sunscreens:
- (A) Organic sunscreen
Organic sunscreens are further divided into UVB and UVA filters:
1. UVB filters
- PABA derivatives – Padimate O
- Cinnamates – Octinoxate, Cinoxate
- Salicylates – Octisalate, Homosalate, Trolamine salicylate
2. UVA filters
- UVA filters
- Benzophenones (UVB and UVA2 absorbers) – Oxybenzone, Sulisobenzone, Dioxybenzone
- Avobenzone or Parsol 1789 (UVA1 absorber)
- Meradimate (UVA2 absorber)
(A) Inorganic sunscreen
- Zinc oxide
- Titanium dioxide
- Others – iron oxide, red veterinary petrolatum, kaolin, calamine, ichthammol, talc
Inorganic agents function by reflecting, scattering or absorbing UV radiation. Their opaque nature and “whitening effect” are an inherent disadvantage, which may be minimized by the use of micronized or ultrafine particles.
Recommendations for Sunscreen Application
Sunprotek should be applied properly to all sun-exposed areas (in a concentration of 2 mg/cm 2), and allowed to dry completely before sun exposure. It should be reapplied every 2 hours, and after swimming, vigorous activity, excessive perspiration, or toweling.
“Teaspoon rule”: 3 mL (slightly more than half a teaspoon)
- for each arm
- for the face and neck
6 mL (slightly more than a teaspoon)
- for each leg
- for the chest
- for the back
- Sunscreen use in infants
Although not known to be hazardous, the use of sunscreens is not recommended for infants younger than 6 months.
- Contact dermatitis
The most common cause of contact dermatitis (photoallergy) among sunscreens is oxybenzone.
- Nanosized particles
Nanosized particles range in size from 1-100 nm. Microfine forms of zinc oxide and titanium dioxide have a particle size of 20-50 nm. Nanotechnology makes inorganic sunscreens more cosmetically acceptable (less whitening of skin after application). In recent years, there have been concerns that nanoparticles can induce free radical formation in the presence of UV radiation. However, studies show that these particles remain on the surface of the skin or in the stratum corneum, and are hence safe for human use.
- Vitamin D production
UVB radiation is responsible for more than 90% of vitamin D production in the skin. It is said that a few minutes of exposure of the face, arms, and hands to noonday summer sunlight two or three times a week is sufficient for vitamin D synthesis.  There have been concerns that widespread use of sunscreens, particularly those with high SPF, may lead to a significant decrease in vitamin D production. However, there is evidence that though sunscreens can significantly reduce the production of vitamin D under very strictly controlled conditions, their normal usage does not generally result in vitamin D insufficiency. In fact, vitamin D and calcium levels have been found to be relatively normal in xeroderma pigmentosum patients, in spite of strict photoprotection.
- Hormonal effects
Some sunscreens (oxybenzone, avobenzone, octinoxate, padimate O) have been tested for their estrogenic/anti-androgenic properties in animal studies. However, the endocrine effects of these agents remain controversial, warranting further human studies.
New Sunscreen Technologies:
Active sunscreen ingredients are entrapped within a silica shell, as a result of which, allergic or irritant reactions to the active ingredient can be minimized, and incompatible sunscreen ingredients can be safely combined, without loss of efficacy.
Sunprotek is the first time in India gel-based sunscreen with unique water-oil-water encapsulation nanotechnology for better spreadability and uniform protection.