Pearl, you sound like an awesome big sister! Your little sister is really lucky to have someone like you watching out for her and helping her to learn about her own health. Taking her to the doctor AND making sure you understand the truth yourself is a winner combination. It sounds to me that you really are on the road to becoming a great Pediatrician

Infections by worms have been recognized since antiquity. Treating some of these infections was among the few notable successes of early doctors. Physicians adopted as their professional symbol a staff encircled by two worms. This symbol, the caduceus, is used to this day.

One of the more obvious worm infections was one which we today call cutaneous larva migrans. As the worms travel through the body just under the skin, scaly red lines mark their paths. These lines are actually inflammatory reactions to the worms.

A very similar skin finding, with raised scaly rings instead of straight lines, was also noted in antiquity.

This infection came to be called ringworm, since the worms apparently traveled in laps around a short circle, rather than in a wandering line. Ringworm typically lasted several months and then, thankfully, resolved on its own. The infection was known to be mildly contagious, but the worm itself was never seen. It was a great mystery.

Some people thought that the ringworm skin lesions looked rather like the holes made in garments by moths -- flat in the center, with a raised border. During the Middle Ages physicians began calling this infection tinea, the name of a common family of moths. Physicians added a descriptive word to the name to specify where on the body the infection was located: ringworm infections on the head were called tinea capitis, on the body tinea corporis, on the feet tinea pedis. They also had specific names for the same infection found in the groin, armpit, facial hair, or nails.

It was not until 1837 that the true cause of ringworm was found. A Polish physician looking at scrapings from the skin of people with ringworm identified a fungus (that he then massaged into his own arm!). Over the next several years, a number of investigators proved that what we call ringworm is always a fungal infection. This was the first time that any microscopic organism was ever proven to cause human disease. It has no connection at all with worms, other than the similar appearance of the skin lesions.

Fungi are tiny plants that survive by eating plant or animal material. The ringworm fungi feed on keratin -- the material found in the outer layer of skin, hair, and nails. These fungi thrive best on skin that is moist, hot, and hidden from the light. When this infection is found on the feet, it is commonly called athlete's foot; when it is found in the groin it is commonly called jock itch; and when it is found on the body it is still called ringworm. Up to 20 percent of the population has one of these infections at any given moment.

Ringworm is very mildly contagious. It can be caught from domestic animals (especially dogs and cats) as well as most farm animals. The infection can be caught from the animal directly, or from anything the animal rubs against (yes, Pearl, your sister could have gotten it from playing on the ground at the BBQ).

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