As I mentioned in my previous article https://drankitasangwan.com/2020/04/08/mastering-the-science-of-sun-protection-why-sunscreen-is-your-skins-best-buddy/ on sunscreens, Sunscreens or UV filters are of two types. Chemical UV filters which absorb UV rays and physical ones that reflect UV rays from skin surface. Next time you pick up that fancy sunscreen bottle from a shopping aisle, read up the label well and choose wisely.
UV filters approved by US FDA.
The UV filters approved by US FDA undergo rigorous testing and standardisation methodology. It makes a lot of sense to choose a product with a body of science and research behind it .
I am listing the chemical and physical UVB and UVA blockers, save up the list for your future reference to help you decide on the best sunscreen for you.
Do keep in mind a few things like UVB mainly leads to sunburn and tanning while UVA leads to aging and tanning. Also SPF is more indicative of UVB blocking capacity while Protection from UVA is separately mentioned as PA +++. An ideal broad spectrum sunscreen has both UVA and UVB blockers and should be applied in adequate amounts to be effective.
CAN A SUNSCREEN GIVE YOU AN ALLERGY OR ANY OTHER ADVERSE REACTION ?
Unfortunately Yes . Most of UV filters have some propensity to lead to contact dermatitis ; phototoxic, irritant , photoallergic and allergic types.
The most common UV filters that cause adverse effects are benzophenones and dibenzoylmethanes, this is the reason PABA as sunscreen has been banned .
Endocrine dysfunction of the reproductive and system is also one of the feared adverse implications of sunscreen usage. An anti-estrogenic effect was strongly associated with BP-3 as well as 3-BC, 4 MBC, and OMC. This translates to delayed puberty, hormonal imbalances in both males and females , possible adverse effects on fertility as well as other receptor level imbalances .
Another concern with sunscreen usage is possible Vitamin D deficiency on long term, but studies have shown that there is no such effect on Vitamin D levels in the body.
For suspected allergic reactions to sunscreens , patch testing by a dermatologist is a good way to know which UV filter is causing the contact sensitivity and accordingly avoiding the agent in future& instituting therapy for the ongoing reaction.
Physical sunscreens are comparatively safer than chemical ones owing to the inert & more photostable nature, however the nano particles (preferred in cosmetic formulations for their better cosmetic feel & less cast formation) can lead to higher penetration across the skin and resulting in free radical damage to skin cells as well as allergic/ autoimmune reactions.
Some chemical UV filters e.g. OMC, Benzophenone-3, 4-MBC can pass through placenta and breast milk , and have significant risk of endocrine disruption so should be used with caution in Pregnancy & breastfeeding.
Infants below 6 months of age should avoid sunscreen use as much as possible unless prescribed by a doctor and if at all they use, it should be on few areas and not on a frequent basis.
Now coming to the Chemical and Physical UV filters commonly used in sunscreens & few other ingredients on your sunscreen label
👉🏻 PABA : is a very good UVB filter , it’s use has been discontinued due to high chances of photoallergy & contact allergy.
👉🏻 Padimate O: PABA derivative, good safety profile , effective UVB blocker
👉🏻 Octinoxate (OMC ) : Cinnamate group UVB blocker , less potent & less photostable than Padimate O.
👉🏻 Cinoxate : UVB blocker from Cinnamate group.
👉🏻 Homosalate & Octisalate : Salicylate group of UVB blockers , weaker than other agents , work to increase the efficacy & photostability of other blockers. FDA approved
👉🏻 Trolamine salicylate : water soluble salicylate UVB blocker.
👉🏻Octocrylene : Very safe UVB blocker, least allergy and irritation potential
👉🏻Ensulizole : water soluble UVB blocker
👉🏻 Camphor derivatives : are moderately effective UVB blockers; not USFDA listed ; e.g. MethylBenzidineCamphor ( 4-MBC)
👉🏻 Oxybenzone : Benzophenone UVA blocker; high contact & photoallergy potential ; possible carcinogenic and endocrine disruptive action . Unfortunately the most commonly used Chemical UV filter.
👉🏻 Sulisobenzone & Dioxybenzone : Benzophenone group UVA blocker , better than Oxybenzone
👉🏻 Avobenzones : broad spectrum & high efficacy UVA blockers ; very photounstable ; degrades other UV filters as well. Always used combined with other UV filters like Zinc Oxide , octocrylene , salicylates
👉🏻Ecamsule : camphor derivative that contains tetraphthalyidene di camphor sulfonic acid, which is a highly stable UVA & UVB blocker, water resistant & good safety & efficacy profile.
👉🏻 MBBT & BEMT : methylene-bis-benzotriazolyl tetramethylbutylphenol (MBBT) and bis- ethylhexyloxyphenol methoxyphenyl triazine (BEMT) are broad spectrum photostable sunscreens, large molecular size precludes systemic absorption or endocrine side effects . Works both as chemical and physical sunscreen.
👉🏻 Zinc oxide : physical UV blocker; reflects away UV rays , photostable ; more effective UVA >UVB blocker ; mainly UVA 1 type blocker .
👉🏻 Titanium oxide : physical UV blocker , UV2 & UVB blocker , ideally combined with other filters like Zinc oxide
👉🏻 Topical antioxidants e.g. Vitamin C , E , polyphenols (green tea), milk thistle extract ( silymarin) : neutralise free radical damage due to UV rays induced Reactive Oxygen Species ( ROS) ; anti inflammatory & anti carcinogenic.
👉🏻 Taurine & Ectoine : Osmolytes working on cell stability during stress.
👉🏻 Silica & Dimethicone : for coating miscronised particles of Zinc oxide & titanium oxide to stabilise them.
There are many other chemicals added to a sunscreen formulation which work as stabilisers and preservatives e.g. parabens, benzyl alcohol, phenoxyethanol etc . These ensure that the sunscreen stays stable and active till its expiry date and does not degrade before that.