What is the first line of treatment for acne?

OTC treatments. Topical treatments include over the counter products containing salicylic acid, benzoyl peroxide or a combination of both. In addition for pustules and cysts heat producing home units can work like a laser in shrinking these lesions. A change in diet avoiding sugar and simple carbohydrates is often useful long term.
See below. I would start out with an over-the-counter benzoyl peroxide cleanser and cream for mild cases. For more severe cases, the first line of treatment would be a prescription for oral doxycycline.