What it means: Probably gout. Yes, that old-fashioned-sounding disease is still very much around -- and you don't have to be over 65 to get it. Gout is a form of arthritis (also called "gouty arthritis") that's usually caused by too much uric acid, a natural substance. The built-up uric acid forms needlelike crystals, especially at low body temperatures. And the coolest part of the body, farthest from the heart, happens to be the big toe.
"Three-fourths of the time, you wake up with a red-hot swollen toe joint as the first presentation of gout," says podiatrist Andersen.
More clues: Swelling and shiny red or purplish skin -- along with a sensation of heat and pain -- can also occur in the instep, the Achilles tendon, the knees, and the elbows. Anyone can develop gout, though men in their 40s and 50s are especially prone. Women with gout tend to be postmenopausal.
What to do: See a doctor about controlling the causes of gout through diet or medication. A foot specialist can help relieve pain and preserve function.