Is SPF 100 worth the hype, or is it just a sticky situation?

With the heatwave and vacation season, interest in sunscreen is at a record high. Despite this, many people are unaware of what the numbers on sun protection products mean. We tend to think that a higher number means "greater control." However, the number next to the SPF does not indicate the strength or duration of protection.

The number referring to the SPF filter correlates with the time you can spend in the sun without burning compared to the time you can spend in the sun with the SPF filter. Dermatologist and skin cancer specialist Dr. Ross Perry explained this to metro.co.uk. He clarified, "If you would burn after 15 minutes in the sun without protection, an SPF 30 would give you 30 times that protection – so around four to five hours in the sun without burning."

Dr. Perry added, "SPF 100 generally just means that it would give 100 times the protection of what a normal burn time would be." Determining how quickly you burn without a filter is not easy. The dermatologist emphasized, "Everyone is individual; one person may burn after 10 minutes while another may burn after 20 minutes, so one person may need to reapply after two hours while another needs to reapply after three."

Human error plays a huge role in the effectiveness of sunscreens. Dr. Perry explained, "It is never the case that coverage will last exactly 100, 50, or 30 times the burn times as people sweat, wash SPF off in pools or the sea, or rub it off against clothing." This, of course, reduces the effectiveness of the products for sun exposure.

Research has confirmed the validity of using SPF 100 filters compared to lighter filters. For example, a 2018 study involving 200 participants applying SPF 50 or SPF 100 before six hours of sun exposure showed that as many as 55% of people wearing SPF 50 had signs of sunburn, compared to only 5% of SPF 100 users.

The dermatologist explained that there is minimal difference between the filters in blocking UVB radiation, which can penetrate the highest layers of skin, causing burning, peeling, and blistering. Dr. Perry informed, "SPF 100 is normally about 99% efficacious in terms of its sunblock, whereas SPF 50 is 98% and SPF 30 is 97%." He added, "As you can see, there is not a great deal of difference between them."

Meanwhile, dermatologist Dr. Mary Sommerlad emphasized, "Very pragmatically, SPF 100 lets in less UVB than traditional SPFs so if you are prone to burning, the more protection the better. However, 1% of UVB still will get through and in intense sunlight this can still be enough to lead to sun damage to the skin."

SPF 100 does not mean total protection from the sun, and considering how much harder it is to find than lower SPFs like 50 or 30, Dr. Perry argues that it is better to wear lower protection and be meticulous about reapplication. Regularly replenishing protection will also be easier for lower SPF filters because SPF 100 formulas can be very thick and sticky and somewhat more effective.