What You Need To Know About SPF, Sunburns + Skin Cancer

I would say it’s hard to believe that summer is right around the corner, except that Laurel and Violet are in full end-of-school-year-giddy mode AND just yesterday I booked the last week of camp I needed for Violet this summer (WHERE IS MY MEDAL, GUYS? That was super hard!). But in all seriousness, how much do you know about skin protection and the dangers of sun exposure? Even though the sun feels great after a long winter, sunscreen is critical (and not just seasonally). I was thrilled to have the opportunity to get some key questions about SPF, sunburns, and skin cancer answered by Chief of Dermatology at Tufts Medical Center, Dr. Clarissa Yang. I am not too humble to admit that I totally did not understand the meaning of SPF numbers previously!

How does SPF work?

When using sunscreen, the SPF (Sunscreen Protection Factor) is a ratio of how much longer you can stay in the sun without getting sunburned. For example, if you sunburn in 1 hour, application of SPF30 would theoretically allow you to stay in the sun for 30 times as long (so, 30 hours) without burning. However, between sweat, exercise, wiping or rubbing against a towel, going in and out of the water, plus some of the enzymatic degradation in the skin, sunscreen breaks down quickly and no longer holds that 30x longer effectiveness (see my recommendation on reapplication next).

How high of an SPF should we look for and how often should it be applied?

Look for sunscreens with at least an SPF 30 and apply 30 minutes prior to going outdoors. Try to stay out of the direct sunlight between 10AM and 4PM, which is when the sunburn rays are the strongest. It is important to reapply at least every two hours and always after swimming or heavy sweating/exercise.

Can I use a tanning bed even if it’s just for a base tan?

No. Even use of one sun tanning bed exposure has increased risk of skin cancer development.

Why is it important to prevent sunburns? 

Sunburns increase your risk of skin cancer and aging.

What are skin cancer risk factors?

You are most at risk for developing skin cancer if you have a history of multiple sunburns. Other risk factors include:

  • You have blue or green eyes with light skin

  • You have a family history of melanoma

  • You have a history of chronic sun exposure

  • You have a high number of moles

  • You have had biopsy-proven atypical moles

  • You have a history of tanning bed exposure

If you use sunscreen religiously but have many skin cancer risk factors, what else can you do to protect yourself from the sun?

Sun protection with clothing is even better than sunscreen, so cover up when you can. Maintaining a good immune system is also important. You can do this by eating a healthy diet full of antioxidants, and getting plenty of sleep. Using topical antioxidants such as vitamin C, E, ferulic acid and retinoids can help as well.

What are some skin cancer symptoms I should look out for?

There are different types of skin cancer. The most well-known is melanoma, a tumor of melanocytes. Always remember the ABCDE’s of melanoma:

  • Asymmetry

  • Border irregularity

  • Color changes

  • Diameter >6mm

  • Evolution (any changes – itching, bleeding, pain, enlarging)

Non-melanoma skin cancers such as basal cell/squamous cell carcinomas are typically pink lesions that do not resolve.  They get bigger with time and may bleed spontaneously or scale. It is important to note that incidence of skin cancer goes up with age.

Is there a cure for Melanoma/skin cancers?

For many decades, late-stage melanoma had a low survival rate - only 6-10% survived within a five year timespan.  However, in the last eight years, there have been significant advances in treatment options in immune and targeted therapy for melanoma. This has made significant differences in patient survivals; however, it is still so important to catch it early. When caught in the early stages, skin cancers are curable through surgical excision, so make sure to do regular self-checks and to schedule annual skin screenings.


Tufts Medical Center is a renowned not-for-profit academic medical center in downtown Boston. Floating Hospital for Children is the full-service children’s hospital of Tufts Medical Center. Both are the principal teaching hospitals of Tufts University School of Medicine. Tufts MC and the Floating Hospital offer a full range of services including primary care, OBGYN services in all areas of women’s health, and dedicated pediatric and adult emergency rooms.

Disclaimer: The content provided in this post is intended solely for the information of the reader. This information is not medical advice and should not replace a consultation with a medical professional.

Disclosure: This post reflects a compensated editorial partnership. Personal commentary by Christine Koh is, of course, her own!

What you need to know about SPF, sunburns, and skin cancer

What you need to know about SPF, sunburns, and skin cancer