Is it possible that i take a child with environmental allergies outside?

That's the goal : Depending on what your child is allergic to and how well his allergies are treated. The goal of treatment is to let him do things that he would not otherwise can't. During winter time like right now, there are not many allergens outside so it is probably fine to let him go outside. If he has asthma, cold air can exacerbate his symptoms. We allergist are specialized in treating those conditions.