When sunny days arrive, sunscreen becomes a must-have. However, myths and misinformation can create confusion about its effective use and the importance of vitamin D. Rachel Neale, a skin cancer expert from QIMR Berghofer Medical Research Institute in Australia, spearheads clinical trials exploring the relationship between sun exposure, skin cancer, and sunscreen efficacy. She has also guided the development of a new drug. Her position statement emphasizes the need to balance sun exposure’s risks and benefits. Here are five key insights about sunscreen every individual should know.

Sunscreen as Your Last Line of Defense

Many believe that applying sunscreen thoroughly and reapplying it every two hours makes them safe to sunbathe freely. This assumption can be misleading. Even high-quality sunscreen allows some ultraviolet (UV) light to penetrate the skin. Prolonged sun exposure can lead to skin damage, even if you reapply. Thus, while it’s important to apply more sunscreen after sun exposure, the damage may already be done.

Relying solely on reapplication every two hours for protection can be deceptive. Supplement your sunscreen use with hats, sunglasses, rash guards, and other protective clothing. Consider sunscreen your last line of defense for areas prone to sun exposure that are hard to cover, such as the hands and neck.

Scientific Evidence Supports Sunscreen’s Efficacy

A pivotal study conducted in Nambour, Australia, evaluated sunscreen’s long-term benefits. In 1992, 1,600 participants were assigned to apply sunscreen daily or use it minimally. Findings indicated that daily sunscreen use halved the risk of melanoma compared to the control group over many years.

The study also showed significant skin damage observations in participants who did not use sunscreen regularly. Those who applied sunscreen consistently experienced a notable decrease in skin aging and reported a slight reduction in overall mortality rates during the 2014 follow-up assessment documented in the findings.

Select the Right Sunscreen for You

Don’t let your sunscreen gather dust—choose one that you enjoy using. If you plan to spend a day outdoors, opt for a sunscreen with SPF 50 or higher. If your outing is brief, SPF 15 or 30 might suffice. Tinted sunscreens can provide equal protection, but ensure they are applied generously. Often, they appear overly pigmented, leading to inadequate application; consider layering a regular sunscreen beneath it.

Chemical sunscreens, containing organic compounds like octocrylene and avobenzone, absorb UV light and convert it into harmless heat. In contrast, mineral sunscreens use zinc oxide or titanium dioxide to reflect UV light. Interestingly, research indicates that mineral sunscreens can also absorb some UV rays, akin to their chemical counterparts.

Achieve Optimal Coverage with Two Layers

The SPF level advertised only applies if you spread 2 milligrams of sunscreen per square centimeter of skin—roughly 7 teaspoons for full-body coverage on average. However, applying this amount at once can be challenging. One strategy is to apply an initial layer, allow it to absorb, and then follow with a second application to ensure full coverage.

I grew up in Armidale, Australia during the 1960s. Despite having fair skin, I rarely used sunscreen as a child and faced three incidents of skin cancer, the first at age 29. Now, I prioritize my skin’s protection.

Vitamin D and Frequent Sunscreen Use

Our recent trial, the Sun-D Study, assessed whether daily application of SPF 50+ sunscreen influences vitamin D levels. Participants were divided to either apply sunscreen consistently or use it at their discretion. Results showed that participants using sunscreen daily had a significantly higher rate of vitamin D deficiency—about 46% vs. 37% in the control group. Those who consistently wear sunscreen should consider vitamin D supplementation, especially during winter months.

Additionally, individuals with darker skin are at a greater risk of vitamin D deficiency. A recent position statement I contributed to discussed balancing the respective risks of sun exposure. It concluded that darker-skinned individuals might not need sunscreen for outings shorter than two hours during high UV conditions, considering their significantly lower melanoma rates and the potential for vitamin D deficiency.