Dense pimples after playing hydrafacial injection may be caused by allergy, improper care and other reasons. 1. Allergy: patients who have sensitive skin or are allergic to the drugs in the hydrafacial injection will have dense pimples on the surface of the skin, accompanied by varying degrees of itching, redness, swelling, tingling and other manifestations. 2. Improper care: after playing the water light injection if improper care, such as injection site premature water, local hygiene is not in place, etc., may be secondary to bacterial infection, so that the surface of the skin appeared a large number of dense pinpoint pimples or edematous erythema, which may be accompanied by itching, swelling, burning sensation and other manifestations. After playing the water light needle up dense small bumps, patients if the symptoms are serious, it is recommended to go to the hospital in time for treatment.