A: According to Clemson University, garlic is marketed in several products intended to repel insects, such as capsaicin. Remember capsaicin is in pepper spray which is used to deter dogs. It is derived from hot peppers. Both garlic and capsaicin have shown an ability to deter insects and both products are labeled to repel a wide variety of pests on ornamental plants. However, they also have been show to repel and harm beneficial insects such as bees. To date there is little research showing effectiveness of garlic insecticides. Products containing garlic or garlic oil include Garlic Barrier and Mosquito Barrier.