Warns Players Of Bart Scott's Advice

Josh Allen might wanna avoid taking Bart Scott's advice and poppin' Viagra before Saturday's playoff game ... 'cause the makers of the blue pill are warning NFL players to talk to a doctor before using their product.

A rep for Viagra tells TMZ Sports the medicine should only be used for its intended purposes ... even if Scott swears it'll help with blood circulation in cold temps.

"Viagra or Revatio, both of which contain sildenafil as an active ingredient, should only be used in the approved indications and always under the supervision of a physician," the rep tells us.

Of course, Viagra is known to help men in another department ... which is why Scott's comment on ESPN's "Get Up" earlier…