If any infection or ailment gets out of hand, or looks like it might, get to a lower elevation as soon as possible – as all problems will be worse at higher altitudes – and contact a physician. Some problems may even disappear at lower altitudes. Remember, too, not to get too cold, tired, sweaty, or over-extended on a hike.
Take it easy, climb slowly. The air is thinner at higher altitudes, making it easier to get sunburned. Drink a lot of water and use more salt to prevent dehydration.