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Dermatology 101: From sunblock to tattoos with On Call with the Prairie Doc®

On Call with the Prairie Doc®

This interview is from SDPB's daily public-affairs show, In the Moment, hosted by Lori Walsh.

The Skin You’re In

By Debra Johnston, M.D.

Skin is the largest organ in the human body, but it’s easy to take it for granted. Unless we notice pain or itching or funny spots, most people don’t give it much thought.

However, the skin is critically important. It helps regulate our body temperature and fluid and electrolyte balance. It provides us critical information about our environment, and it protects us from invasion by the sea of germs we encounter every day. Some of the sickest patients doctors ever treat are those who have had significant skin loss, whether due to illness like toxic epidermal necrolysis, or injury like burns.

This important organ can give doctors clues to diseases elsewhere in the body. Rashes might suggest celiac disease, or an overactive immune system, or internal cancers. Skin discoloration might alert us to liver diseases, hormonal conditions, or dangerous exposures.

The skin itself is subject to diseases. Genetics plays a role in conditions like eczema and psoriasis. Sometimes our habits can set the stage for skin problems. Sun exposure increases the risk of skin cancer, but it also accelerates the development of wrinkles. Smoking does, too.

So, what can we do to protect our skin, especially as summer approaches?

One big step is to protect it from the sun. Sunscreen is very useful! Use one that blocks both UVA and UVB light. Choose SPF 30 or higher, and don’t forget to re-apply every two hours. Most sunscreens break down when exposed to the sun, so even if you are wearing SPF100 it won’t last through the afternoon. Sunscreen takes about 15 minutes to bind to your skin and protect you, so put it on before you head out. Use enough: the average adult needs at least a shot glass worth for each application. One bottle might not last your family through the whole weekend at the lake. Water resistance is useful, but sunscreen is never truly waterproof, so re-apply after swimming or sweating. Ultraviolet light penetrates cloud cover, so sunscreen is important even on overcast days. Don’t forget your lips: many skin cancers develop there, so wear lip balm with SPF.

Sunscreen isn’t the only protective measure you can take. Consider the tried-and-true approach of covering up. Wear long sleeves and wide brimmed hats. Stay inside, if you can, especially during the parts of the day with the most direct sunlight.

Your skin has a big job, protecting you from the environment. You can return the favor, and protect it, too.

Debra Johnston, M.D. is part of The Prairie Doc® team of physicians and currently practices family medicine in Brookings, South Dakota. Follow The Prairie Doc® at and on Facebook featuring On Call with the Prairie Doc® a medical Q&A show celebrating its twentieth season of truthful, tested, and timely medical information, broadcast on SDPB and streaming live on Facebook most Thursdays at 7 p.m. central.

Lori Walsh is the host and senior producer of In the Moment.