All of a sudden my left eyelid had a lump now its swollen all the way. and i have.allergies what can be the cause of this ? and how long will it last

Infection likely: A lump in the eyelid is often a stye or chalazion, which is a blockage of an oil gland in the lid. However, if the whole lid becomes diffusely swollen and tender, then it is probably infected (cellulitis), and this should be promptly treated, usually with oral and topical antibiotics. Sometimes allergies could cause lid swelling, but not usually just on one side.