If you don't have any medications, to avoid throat infection. what can you buy (at the pharmacy) or do?

Try sinus rinse: You can get a Netipot and do regular sinus rinses with salt water. Great for allergies as well so you will have less postnasal drip and hence less sore throat

Kleenex!: There is really no medicine to avoid throat infection> Such infections, called pharyngitis or tonsillitis, are mostly viral , and occasionally from strep bacteria. If you have symptoms of itchy or sore throat, you can take oTC medicine like lozenges or pain killers like Acetaminophen or ibuprofen. Check with your physician if u suspect strep or symptoms persist beyound a week or so.