A West Perth man is facing charges after five people unwittingly ate brownies laced with marijuana at a gathering in Mitchell.

Police say they were contacted by a male who fell ill after a meal at a gathering in early March and medical tests showed the man tested positive for THC, the primary intoxicant of marijuana.

Another four people at the gathering also experienced physical illness, with medical tests confirming the presence of THC. All five have since recovered.

An investigation determined that brownies left out for dessert were the source of the THC and the individual who brought the brownies was identified.

As a result, 42-year-old Colin Wood has been charged with five counts of administering a noxious thing and trafficking in a Schedule II substance.

He is scheduled to appear in a Stratford court Thursday.