There are a number of steps that you can take to combat your acne.
You should try first with OTC topical ointments. There are two main types of anti acne ointments which are both very effective:
Retinoids – Differin gel (OTC) is one of the most useful ointments for this. Higher strength ointments are available on prescription.
BenzoylPeroxide: Benzoyl peroxide dries up the skin and reduces oil thereby helping in curing.
These are OTC ointments available at pharmacies and you can use them on your own. They will help to cure the acne.
Since he has used Duac gel, which is benzoyl peroxide, you can try with the Retinoid now.
If the acne persists after this, you need to show a doctor, preferably a dermatologist. A doctor will be able to prescribe other stronger medicines: Higher strength Retinoid ointments, Antibiotic topical ointments, Oral antibiotics, Accutane, Steroids, etc.
But first, you can try OTC treatment with ointments as I suggested.
You should also follow a good skin care regime. At night, first clean your face with soap and water. Apply an astringent. Then apply the acne medicine. Lastly apply a moisturizer gently. Follow this every night. This will help you greatly.
Avoiding the sun is most important. Wear a wide brimmed hat or a cap with a peak when going out in the sun. Using suncream with above 50% SPF is a must. This helps greatly.
This OTC regime should be sufficient, but if the acne persists, you need to show a Dermatologist.
Hope I have been able to clarify the situation for you and helped in resolving your query.
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Dr. P. Jyoti