Started augmentin (amoxicillin and clavulanate) 875mg twice a day for 10 days for sinus infection how long till it clears up on day 4. also can you have allergie sinus issues also?

Usually 36-48 hours: The Augmentin (amoxicillin and clavulanate) starts helping in about 2 days but you may not notice a huge difference in how you feel for up to a week if you had a lot of congestion in the sinuses. Allergies do tend to flare sinuses and sometimes need to be treated with a different med. that Augmentin (amoxicillin and clavulanate) alone wouldn't handle. Nasal irrigation with mild saline can help also