Hi, Swollen and redness underneath eyes could be due to allergy. Allergy can be diagnosed by patient s history to the allergens and clinical examination up to some extent but not by any laboratory investigations although there are plenty of allergic sensitivity testing to food,plant,fruits etc is being done noways but none of them is reliable and adds only cost to the patient. If your symptoms developed due to that juniper and cypress trees and get subsided by antiallergics then one can say it was due to allergy. The best way to combact allergy is to avoid contact with allergen although there are good antiallergic drugs like steroids ( oral,injectable, inhalation, topical forms), antihistamines with mast cell stabilizers are available but none of them cures disease but gives only temporarily relief. You can go through blood immunoglobulins level and consult immunologist for further advise. Hope you understand my point. Thanks.