Uncle got bitten by spider, he is an alcoholic but foot has been swollen for more than 3 months, the type of spider is unknown. any treatment?

He needs to be: Seen and evaluated. Any persistent swelling, especially in an alcoholic needs professional evaluation.

Needs a check up: Your uncle needs to be examined by a physician to find why his foot is swollen. Spider bites do not cause such problems. If spider bite was the cause, it would have resolved in one or two weeks. I suspect he has something else causing this problem. it could be a blood clot or some other medical problem which requires examination and further testing.

Recommend ER: Would have a physician take a look at it. To assess for abscess if it needs to be drained and for the correct antibiotic.