One explanation is that no matter how much sunscreen you use, or how high the SPF number, some UV rays will still reach your skin. To break it down, an SPF 15 guards against 93% of UVB rays, SPF 30 protects against 97% and SPF 50 blocks out about 98%. Besides, people who don’t wear SPF year-round are often deficient in vitamin D, too.

The consensus among many experts is that supplementing vitamin D is just as good as sun exposure. “The recommended daily intake of vitamin D as per the National Institutes of Health (NIH) is between 400-800 IU (international units) daily, or 10-20 micrograms daily,” says Claire Shortt, nutritionist and lead scientist at FoodMarble. Good options include Artah Essential D3/K2 and Wild Nutrition Food-Grown Vitamin D, or BetterYou D1000 Vitamin D Daily Oral Spray if you prefer a spray over a tablet.

You can further boost your levels by including egg yolks, oily fish such as salmon and mackerel, as well as dairy that is fortified with vitamin D, in your diet.

Is SPF30 better than SPF50 in winter?

The answer to this depends on several factors, including your skin type and concerns, if you’ve had skin cancer, are on medication or travelling abroad.

SPF is a measure of protection from UVB rays. “For UK winters, SPF30 is sufficient for most people as long as the filters are good,” says Dr Veraitch.

According to Dr Sommerlad, on a normal wintery day, the focus should be on choosing a facial sunscreen with a high UVA rating (typically marked by the letters “UVA” within a circle or a PA++++ rating) to protect against hyperpigmentation (clover-shaped brown splotches on the skin) and damage to your skin’s DNA, elastin and collagen (the springs and stuffing of your skin).

Asked whether a moisturiser with added SPF would suffice, Dr Veraitch told Glamour: “Most standalone SPFs are formulated much like moisturisers, but they offer more reliable protection than moisturisers with added SPF.”

If you’re going skiing, however, you will need up your sunscreen game and regularly reapply an SPF50+ as snow reflects up to 80% of the sun’s light. “These rays are more likely to be directed at exposed skin,” says dermatologist Dr Alexis Granite. “UV exposure is even stronger at higher altitudes because the atmosphere is thinner, providing less protection.”

On the slopes, Dr Granite recommends being as diligent when slathering on a high factor sunscreen as when you’re on the beach in the height of summer. “Apply sunscreen early in the morning but, when out skiing all day, it’s important to reapply sunscreen every 2-3 hours,” she says.

Likewise, “if you have a history of skin cancers, or are taking medications that make you prone to burning, stick with an SPF50 in the winter months regardless of the fact that UVB is less intense,” adds Dr Sommerlad.

How to apply sunscreen in winter?

Step 1: Cleanse as normal.

Step 2: Apply a serum of your choice, whether that’s an antioxidant-rich formula or a more targeted approach using tranexamic acid for pigmentation and niacinamide or azelaic acid if you’re prone to congestion.