Why sunscreen is a drug (or a natural health product) in Canada

The moisturizer on the shelf has no number on its label. The sunscreen right beside it does: a DIN or an NPN. That’s because, in Canada, sunscreen isn’t a cosmetic at all. It’s a health product that claims to prevent harm, and that changes the rules for what goes in the bottle and what the label is allowed to say.

Why sunscreen isn’t a cosmetic

A cosmetic cleans, beautifies or changes how you look. A sunscreen does something else: it claims to protect your skin from ultraviolet (UV) radiation and help prevent sunburn. Health Canada classifies sunscreens as either non-prescription drugs or natural health products, and both need Health Canada authorization before they can be sold.

That’s also true of a daily moisturizer or foundation with an SPF on the label. Once a product claims a sun protection factor, it’s a sunscreen in the eyes of the regulator, whatever aisle it sits in.

DIN or NPN: it depends on the filter

Which number a sunscreen gets comes down to its UV filters, the ingredients that absorb or scatter UV light.

• NPN (Natural Product Number): products whose only filters are zinc oxide or titanium dioxide, the two mineral filters. Health Canada’s monograph allows each at up to 25%.
• DIN (Drug Identification Number): products that contain any of the chemical filters on the monograph’s drug list, such as avobenzone, octocrylene or bemotrizinol, each with its own maximum concentration.

A sunscreen that mixes a mineral filter with a chemical one gets a DIN.

It’s tempting to read the NPN as “gentler” or the DIN as “stronger”. Neither is built into the number. Both routes lead to the same Primary Sunscreen Monograph, a Health Canada document that sets out the allowed ingredients, the claims, the label wording and the tests. The number mostly tells you which filters are inside.

What SPF means, and how it’s measured

SPF stands for sun protection factor. It describes protection against sunburn, which is caused mainly by UVB rays. Health Canada notes that SPF indicates relative protection from burning; it isn’t a count of how much longer you can safely stay in the sun.

The number comes from a standardized test on volunteers, such as ISO 24444, the international method the monograph names. A measured amount of product is spread on the skin, and researchers compare how much UV light it takes to cause redness on protected and unprotected skin.

Two label rules follow from the monograph:

• Any value above 50 must be written as “SPF 50+”. You won’t see SPF 70 or SPF 100 on a Canadian label.
• No other “+” is allowed, and neither is anything claiming “all day” protection or that the product lets you stay in the sun longer.

The catch is the amount. Standard tests use 2 mg of sunscreen per square centimetre of skin, a thick layer. A study of 40 volunteers, published in 2009, applied the same product at 2, 1.5, 1.0 and 0.5 mg/cm² and found the SPF dropped as the amount dropped, with every smaller amount significantly lower than the full one. The authors’ conclusion was simple: people need to apply more. Health Canada’s guidance for adults is about 35 mL for the whole body, roughly a teaspoon each for the face and neck, each arm, each leg, the front and the back.

What “broad spectrum” means on a Canadian label

Health Canada explains that UVB is the main cause of sunburn, and that both UVA and UVB can increase your risk of skin cancer. Broad-spectrum sunscreens protect against both.

To use the words “broad spectrum”, a product must contain filters that cover both UVA and UVB and must reach a critical wavelength of at least 370 nanometres. That’s a lab measurement of how far into the UVA range the product’s protection extends. The monograph points to standard methods such as ISO 24443 for the UVA testing.

A sunscreen that wants to say it helps reduce the risk of skin cancer has to meet more: SPF 15 or higher, broad spectrum, and a full statement on the label about other sun protection measures. Health Canada itself recommends broad spectrum with SPF 30 or higher.

Water resistant, not waterproof

This is the claim people misread most.

The monograph allows a product to say it’s water resistant or sweat resistant for 40 minutes or 80 minutes, and only if it passes a recognized water resistance test. Those minutes are the tested time in water, so they’re a reapplication timer, not a promise that the sunscreen stays put all afternoon.

Words that suggest otherwise aren’t permitted: “waterproof”, “sweat proof”, “sunblock”, “sun shield” and anything implying total or complete protection.

Health Canada’s general directions are to apply generously at least 15 minutes before going out and reapply at least every two hours, and more often if you’re sweating, swimming or towelling off.

Does Health Canada check sunscreens after they’re sold?

Sometimes. In 2017, after a spike in reports of skin reactions following media coverage, Health Canada tested 27 sunscreens with chemical filters, 18 of them marketed for children. It checked pH, the amount of each active ingredient, undeclared ingredients, two specific preservatives, and microbial contamination. All 27 passed. A follow-up safety review concluded that rare, mild to moderate skin reactions can occur in people allergic to specific ingredients, a risk already covered in Canadian sunscreen labelling.

That’s the honest picture: authorized sunscreens are generally made as labelled, and reactions are uncommon, but they happen. If a sunscreen gives you a rash, stop using it and ask a pharmacist about one with different filters. For babies under six months, Health Canada suggests asking your health care provider before using sunscreen.

Reading the label in 30 seconds

• DIN or NPN? One of them should be there. If a product claims SPF and has neither, be cautious.
• SPF 30 or higher, and the words “broad spectrum”.
• Water resistant for 40 or 80 minutes if you’ll be swimming or sweating.
• The expiry date. Health Canada notes every sunscreen has one.

In short: Canadian sunscreens are health products, with an NPN for mineral-only filters and a DIN for chemical ones. Both follow the same monograph, which standardizes SPF testing, reserves “broad spectrum” for products that cover UVA as well as UVB, and swaps “waterproof” for a tested 40 or 80 minutes. The label is reliable; the part that’s up to you is using enough and reapplying.