Swelling of the face after hair dyeing is considered to be an allergic swelling caused by skin contact due to an allergy to the ingredients of the hair dye. It is recommended to first remove the allergen and wash the hair, especially the hair dye stained on the scalp should be washed as clean as possible. If the swelling of the face is mild and there is only a slight itching sensation, you can use a wet compress such as cypress liquid, and then apply basic moisturizing skin care products, and try not to rub other efficacious products to avoid irritation. You can take oral antihistamines, like loratadine tablets, cetirizine hydrochloride tablets, chlorpheniramine maleate tablets, and ibastine tablets, which have a sedative and anti-itching effect and can reduce swelling. If the swelling of the face is more serious, accompanied by obvious itching, heat and pain in the face, it can be treated with glucocorticoids, such as dexamethasone and prednisone. All of the above drugs need to be used under the guidance of a doctor, do not use them without permission. During the period of allergy, the diet needs to be careful not to eat river food, seafood, and spicy and irritating foods such as chili and leek to avoid aggravating the allergic reaction. If the swelling of the face does not subside, or even tends to increase, you need to seek medical attention immediately.