United went up 1-0 on 17-year-old rookie Andy Najar's fifth goal of the season. Houston tied it in the 66th minute when Devon McTavish was charged with an own goal after deflecting a shot past Perkins.
After Cameron's goal in the 70th minute, Dominic Oduro added a goal in second-half stoppage time to close out the scoring.
The Dynamo improved to 7-14-5) while United fell to 5-18-3.
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