It is getting on to the silly season, and there's no reason to expect our medical friends to be exceptions to hot-weather foolishness.

In the generally staid letters column of the Journal of the American Medical Association, for example, there has been an ongoing controversy over Pthirus pubis. A perfectly valid subject for medical exploration, of course, but a raging controversy?

Pthirus pubis is commonly known as P pubis and even more commonly known as "crabs."

Without going into too much detail, the current discussion, ranging from California to Scotland, has been over the presence of P pubis in the eyelashes of adults and children and how and why they got there. In any case, the main points seem to be these:

* P pubis doesn't go for hair on heads because it is too cold up there for the lice.

* Eyelashes may be a second choice of the pests, but apparently supply a satisfactory environment.

* When eye infections do not clear up, P pubis should be suspected and eyelashes examined under microscopes.

Hair braiding may lead to baldness in black children, according to an article in the May issue of the American Journal of Diseases of Children.

Dr. Gary J. Brauner of the Albert Einstein College of Medicine, New York, wrote that bald spots on the heads of black youngsters are "a common complaint," and the "kinky shape of the hair of blacks" makes it more susceptible to the day-to-day pulling and tugging caused by "multitufted" braiding. The popular "cornrow braiding" does not cause the balding problem, he said, but may lead to increased bacteria growth and infected lymph glands of the head and neck.

The article also warned that "chemical and physical relaxers to the hair tend to weaken it so that subsequent braiding or 'hot combing' may compound the baldness problem."

Oral Rehydration Therapy (ORT), the simple, pre-packaged mixture of sugar and salts that can reverse the potentially fatal dehydration of infants and young children with diarrhea, is getting an international boost from the U.S. Agency for International Development, which now has 71 diarrhea-related projects in 53 developing nations.

The international children's health groups that are its major promoters, however, see lack of funds and education as major blocks to worldwide acceptance of ORT. (There are an estimated 500 million attacks of diarrheal diseases every year and one in 10 children under 5--about 5 million a year or 570 an hour--will die from its ravages, mostly from the dehydration it causes.)

Vice President Bush and Health and Human Services Secretary Margaret Heckler were among officials praising the therapy and deploring the relative slowness of its acceptance at a recent four-day ORT international conference in Washington.

"It has yet to appear in any pediatrics textbook," lamented one international health official.

In this country, the inexpensive pre-measured packet, which must be mixed with water, is sold as "Infalyte."

For pediatricians and parents, an excellent publication on Oral Rehydration Therapy, including recipes for home mixtures, has been produced by the Population Informtion Program of Johns Hopkins University and is available by writing the program: Hampton House, 624 N. Broadway, Baltimore, Md. 21205.

For general information: write United Nations Children's Fund, United Nations, New York, N.Y.

The ubiquitous and often informative ABC between-soaps feature called "FYI" announced pontifically a "new discovery" by "a British researcher" one day last week.

The discovery was that putting a paper bag over your head and "rebreathing" your breath could alleviate migraine headaches.

"FYI" narrator Hal Linden didn't say who the British researcher was or where this "new" discovery was published, but I can tell you that it is a remedy offered to me some 20 years ago by my cleaning woman.

Although I tried it a couple of times, I frankly can't say for sure whether it worked. I didn't have faith. But now that it's been confirmed by the eminent scientific Brits, who knows? It does seem to work for hiccups.

Of course, someone may confuse you with a Feds fan . . .

Women who are taking oral contraceptives are still being recruited for an ongoing study on the relationship of exercise to cardiovascular health, metabolic functions, clotting mechanisms and a host of other physiological activities.

The Uniformed Services University of the Health Sciences is seeking women (taking the pill) who are:

* Relatively sedentary non-runners.

* Moderate runners--somewhere between five and 15 miles a week.

* Marathoners, running more than 50 miles a week.

Especially sought-after for the study are women who may be suffering menstrual irregularites (or suppression) because of their running habits.

The study involves one session, several hours long, at the specially equipped laboratory at the university (next to the Naval Medical Hospital in Bethesda). Women meeting any of the above qualifications should be between 18 and 45, not obese and on no medication except an oral contraceptive.

Those interested should phone exercise physiologist Sue Wigutoff at (301) 295-3623.