Assuming your son is on the young side, say 8-12, then I wouldn’t worry too much about it. The chances are good that wearing pantyhose is just a phase, and he will grow out of it. I’d imagine that he is doing it because he likes the feel of a sheer material on his legs. In no way does this mean that he is gay or somehow perverted, just that he likes pantyhose.
As long as he understands the limits of his behavior, (i.e. wearing hose is an at-home thing, he should be careful discussing what he is doing with his friends, maybe he should wear long pants while he wears hosiery,) and knows that what he is doing may make some people uncomfortable, he should be allowed to express himself in this manner.
You should be, or at least pretend to be, understanding and supportive. If he is made to feel shamed or embarrassed, it could lead to problems later in life. If it makes him happy, let him try this out for a while. Set limits if need be, and don’t worry – lots of people do lots of things that others find…odd.
The 1st answer / advice here given (“Assuming your son…”) is very good. I will just add that there is nothing wrong with this wearing. It is far more common than most people think. Many (not just 2 or 3) Hosiery companies now make / sell Pantyhose strictly for Men.
(also keep in mind, Men wore tights before Women. ) [It is just a society/television/magazines thing now that 99.997% of us sadly follow] Many Men even in the popular media always try to break out and wear Pantyhose in public. This happens every few years. “Grunge” rock music guys starting wearing cargo pants with long underwear, then switched to black tights, then navy or white and some went to sheer Pantyhose. But that was at the end of ‘grunge’ music and we didn’t see much after that. But then it always starts again and again.
If your son told you about this (how you found out) you should be very flattered as so many males wear Pantyhose but rarely tell people, especially family about it.
Not just Men in general but also in the military. Pantyhose (Nylons) are a great defense against blisters, and is taught by the US Air Force to males during cold climates to aid in wicking moisture away from the feet to prevent common foot related problems with too much moisture such as sweat induced trench foot during field exercises.
(Source= Air Mobility Warfare Center, Fort Dix, NJ, 2000)