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Mayo Clinic Q&A: seborrheic keratoses, probiotics versus prebiotics

Old man hands clasped together.

Old man hands clasped together.


I've developed waxy, brown spots on my skin. Are they potentially dangerous? What's the best way to get rid of them?

What you describe may be seborrheic keratoses, commonly referred to as aging spots. Seborrheic keratoses are some of the most common, noncancerous skin growths in older adults. They're not cancerous or precancerous.

Seborrheic keratoses usually appear as brown, black or light tan growths on the face, chest, shoulders or back. The growths have a waxy, scaly, "stuck on" appearance. Occasionally they appear singly, but multiple growths are more common. Their cause is unclear.

Although they may sometimes be itchy, these growths are typically painless and don't require treatment. If they become bothersome or irritated by clothing or you just don't like the way they look or feel, there are several ways a dermatologist can remove them.

One common method, especially if several growths are being removed, is to freeze the growths with liquid nitrogen (cryotherapy). A few days after treatment, the seborrheic keratoses fall off.

Blisters or scabs may develop afterward but this will heal within a few days.

Another option is to apply heat (cautery) to the growth after the area has been numbed. The heat, which comes from an electric charge, softens the growth so that it can be removed with a cotton swab or a scoop-shaped instrument (curet).

Laser therapy is another option, but it's generally more expensive and no more effective than other methods.

Cauterization generally results in darker pigmentation of the treated skin area, whereas cryotherapy usually leads to lighter pigmentation. Talk to your dermatologist about which method may be best for your skin tone.

Lawrence E. Gibson, M.D., Dermatology, Mayo Clinic, Rochester, Minn. (adapted from Mayo Clinic Health Letter)


What's the difference between probiotics and prebiotics?

Probiotics are foods or dietary supplements that contain either good bacteria or certain types of yeasts that provide health benefits. The live microorganisms in probiotics are often similar to those naturally found in different parts of your body, such as your intestines. In functional foods, such as yogurt and kefir, and dietary supplements, the most commonly used probiotic bacteria are strains belonging to bifidobacterium and lactobacillus. These two groups of bacteria are among the legions of microorganisms that reside in your gastrointestinal tract and are known collectively as gut microbiota.

Prebiotics are nondigestible substances that act as food for the gut microbiota. Essentially, prebiotics stimulate growth or activity of certain healthy bacteria that live in your body. Prebiotics are found in whole grains, bananas, onions, garlic, honey and artichokes.

When probiotics and prebiotics are combined, they form synbiotics. Live culture yogurt that hasn't been pasteurized is a synbiotic product. Fermented dairy products, such as yogurt and kefir, are considered synbiotics because they contain live bacteria and the fuel they need to thrive and proliferate.

The influence of probiotics and prebiotics on gut microbiota is under research. Scientists want to know if probiotics reduce harmful organisms in the colon or if they produce substances that destroy or interfere with the growth of microorganisms and influence the immune response. Evidence supports the use of probiotics for certain bowel disorders, including irritable bowel syndrome, antibiotic-associated diarrhea and pouchitis.

Purna C. Kashyap, M.B.B.S., Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minn. (adapted from Mayo Clinic Health Letter)

Mayo Clinic Q & A is an educational resource and doesn't replace regular medical care. Email a question to MayoClinicQ& For more information, visit © 2015 Mayo Foundation for Medical Education and Research. All rights reserved distributed by Tribune Content Agency, LLC.

Mayo Clinic Q&A: seborrheic keratoses, probiotics versus prebiotics 10/15/15 [Last modified: Thursday, October 15, 2015 5:46pm]
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