Effol Horse Fly Blocker Extra strong and extremely effective horse fly repellent spray. The long lasting, ready to use spray has been developed in collaboration with the Swiss Tropical Institute especially to protect against unpleasant horse flies and other troublesome pests. It is also a useful tick repellent. Use of a selected birchwood extract makes it particularly kind to the skin and coat. Contains cat-mint oil, juniper oil, birchwood extract, cedarwood oil and Effol ethereal oil composition.