How long does it take for eye swelling caused by allergy to subside generally depends on the severity of the condition, treatment measures, etc., and needs to be analyzed on a case-by-case basis. Eye swelling caused by allergy can generally subside in 2-5 days under scientific and regular treatment, but the time will be extended accordingly for those with more severe symptoms or those who are continuously exposed to allergens. Eye swelling caused by allergy is usually caused by contact allergy, and it is generally recommended to take antihistamines, such as loratadine and cetirizine, and use them in combination with hormonal eye drops, which have relatively faster and better effects and can achieve rapid reduction of swelling. However, the use of hormonal eye drops for more than 2 weeks has the possibility of triggering glaucoma. Therefore, if the effect is still unsatisfactory after 1-2 weeks of hormone use, it is recommended to promptly consult an ophthalmologist to determine the plan for continued treatment. Chronic allergy sufferers are recommended to have allergen screening test in time to find the cause of allergy and try to avoid contact in life to reduce the chance of allergy occurrence.