An upset stomach, a runny nose or a nagging headache aren't fatal, but these little ailments can certainly annoy.

Today, medical researchers focusing on such routine disorders are finding new twists to old treatments. In some cases, they're coming up with entirely fresh approaches.Ladies' Home Journal recently looked at some conventional treatments and some new remedies for one of life's most persistent health problems: the headache.

Thirty million to 40 million Americans suffer from some kind of headache pain. Twelve million to 15 million have migraines, throbbing headaches marked by intense pain and sensitivity to light that tend to occur only on one side of the head. Until recently, doctors had little to offer beyond the standard advice to take two aspirin. For migraines, they sometimes relied on potentially addictive narcotics such as Demerol.

Experts now say excessive use of pain medications tends to perpetuate rather than cure headaches, because they alter brain chemistry. Doctors are also becoming aware that headache pain is not caused solely by tension but also by chemical changes in the brain.

The latest research suggests the cause of certain headaches is somehow related to serotonin, a naturally tranquilizing brain chemical. One still-experimental medicine with the code name GR43175 may prove to be effective in aborting acute attacks of migraine. Experts don't yet know whether the drug will be helpful against other types of headache.

Doctors can also offer migraine patients the non-narcotic drug Dihydroergotamine (DHE), which acts on the brain to halt pain in a way that's not yet clear.

It's now easier to find comprehensive approaches to curing headaches by going to headache clinics, which are opening across the country. These centers, about 30 so far, offer the expertise of a variety of specialists. Their approaches include drug treatments along with lifestyle modification (exercise, stress reduction and diet). A complete evaluation at these clinics averages $300 to $600, and most insurance companies will reimburse the costs.

-For a list of headache centers, university research centers and specialists, write to the American Association for the Study of Headache, P.O. Box 5136, San Clemente, CA 92672.