1. Control of extrinsic factors : Measures must be taken to avoid causative allergens such as the house-dust mite,pets,moulds and certain food stuff.Pollen avoidance is impossible ,however contact may be diminished by wearing sunglasses. Avoiding walks in the countryside particularly in the late afternoon when the number of pollen grains is highest at ground level.Keeping the bedroom window shut at night also helps. Avoidance of the house-dust mite is now possible with effective and comfortable covers for bedding and changes to living acccomodation.Active and passive smoking should be avoided .