Redness underneath the penis of a 9-month-old baby may be an inflammatory condition, and it is also important to be alert to the presence of hypospadias, allergies, and other conditions. 1. Inflammation: If the infant does not pay attention to washing or cleaning the perineal area after urination, urine residue in the penile area may induce inflammatory conditions to appear. In addition, some parents like to use diapers, and do not change in time, may also lead to similar symptoms. Parents need to raise awareness and pay attention to the maintenance of infant hygiene to promote the symptoms to subside. 2. Hypospadias: This is a congenital defect in which the opening of the male urethra is abnormally positioned, and the urethra does not appear in the central position of the tip of the penis, but rather in the normal urethral orifice to the perineum on the line, and urine flows from the local area, stimulating infants to develop symptoms of redness under the penis. Need to go to the genitourinary surgery department to clarify the condition. 3. foreskin allergy: the foreskin is allergic to contact with allergens, bleeding penis redness, swelling and itching. In addition, 9-month-old infants with red under the penis may also have eczema and other, it is recommended that the parents of the affected children to take their children to the clinic, to clarify the specific conditions before treatment, to minimize the impact of the lesions on the affected children.