The House, amid some confusion, voted 222 to 189 yesterday to forbid the counting of aliens in reapportioning the 435 House seats among the states for the 1982 election.

The seats are divided up every 10 years on the basis of the head count of the decennial census. States gain or lose seats depending on population shifts. For several decades the big northeastern states have been losing seats to the Sun Belt.

Rep. Joseph McDade (R-Pa.) led the fight against counting aliens, whom he estimated at 20 million altogether, most of them illegal and all of them not voting. McDade said counting aliens in allocating House seats dilutes the rights of citizens.

Pennsylvania's 25-seat allocation reportedly stands to be hurt if aliens are counted. This could account for the fact that most speeches for the amendment were made by Pennsylvanians.

There was considerable uncertainty about what the provision would mean if it passed the Senate and became law. Some members said most census forms do not show whether the person counted is a citizen or not, so it might require a complete recount.

Rep. Edward Derwinski (R-Ill.) opposed the amendment, saying no illegal aliens were counted anyway because they all hid from the census takers for fear of being deported. Rep. Tom Steed (D-Okla.) managing the Treasury-Postal Service appropriation bill, said the amendment might prevent reapportionment, but he didn't oppose it, remembering how reapportionment once nearly wiped out his district.

The House approved the bill and sent it to the Senate after also approving an amendment that would forgive income taxes for the American hostages in Iran during their captivity.