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Clinician’s Corner: Sunscreen – The Basics

The Basics on Sunscreens

“An ounce of prevention is worth a pound of cure”, is a well-worn adage we pharmacists use when discussing blood pressure, Type-2 diabetes, and osteoporosis.  With summer rolling in to our part of the nation this is even more applicable with the appearance of much desired sunshine.

Skin Protection Factor (SPF) : how the efficacy of a sunscreen is expressed.  It is a ratio of the time required to produce minimal redness with a sunscreen, to the time to produce minimal redness without a sunscreen.  An SPF of 15 will allow a person to remain in the sun without burning 15 times longer, than if the skin was unprotected. If it takes you 10 minutes to get “burned”, a sunscreen with a SPF of 15 will allow you to be in the sun 150 minutes (2.5 hours) before redness develops.

Here is how sunscreens work:

Chemically: absorb a specific portion of the spectrum thus preventing harmful rays from hitting the skins surface. Examples: PABA, Cinnamates, Ethylhexylsalicylates, Benzopheones.  Most sunscreens contain combinations of 2 or 3 of the classes.

Physically: provide a physical barrier to UV radiation and scatter or reflect the harmful rays. Most commonly referred to as “sunblock” Examples: Zinc oxide, red petrolatum, Titanium dioxide.

An SPF of at least 15 is recommended for most people by the Skin Cancer Foundation.  HOWEVER…

  • Products with SPF over 30 only block UVB slightly more than those of SPF=30. The higher concentration of chemicals increases potential for adverse effects, such as skin rashes.  SPF over 30 are labeled as “SPF 30 plus”.  An SPF of 30 blocks 97% of the UVB rays.  An SPF of 15 blocks 93% of UVB rays.  Higher SPF products do increase the likelihood of allergic reactions.
  • By bumping the SPF from 15 to 30, it may offer an extra margin of safety if do not apply a sunscreen as frequently as indicated.

Whether you are enjoying the sands of Myrtle beach, or Prince Gallitzin State Park, your Thompson Pharmacist can recommend appropriate sunscreens to help protect your skin from the harmful rays of the sun.  At Thompson Pharmacy, it’s all for YOU!