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In simple terms, tylosin is a natural antibiotic made by bacteria. It acts by interfering with the protein manufacturing abilities of other bacteria. It only affects bacterial protein manufacture and thus does not affect protein manufacture by mammals, birds or reptiles. Tylosin is an antibiotic of the macrolide class (same class as erythromycin).


Tylosin is licensed for use in livestock as a broad spectrum antibiotic in treatment of infection but it has other uses that have little to do with its antibiotic activity. In small animals, tylosin is not used as an antibiotic at all but as an anti-inflammatory. Its chief use is for the treatment of colitis. In this situation, it is not used as an antibiotic to treat infection but instead as an anti-inflammatory to soothe the large intestine. While few formal studies have been performed to examine this non-antibacterial property of tylosin, it certainly seems to work in this regard.

Another common use is to reduce tear staining, particularly in white colored dogs. Small breed dogs commonly have shallow tear wells which lead to tear overflow down their face, a condition called "epiphora." The subsequent red-brown staining of the fur from tear pigments is felt to be unsightly and through an unknown mechanism tylosin seems to alleviate this condition; in fact, the Angel Eyes® product listed above is marketed exactly for this use. There are two controversies regarding this use of tylosin. The first is with the Angel Eyes® product itself.

This product is a beef-flavored chewable but the exact amount of tylosin is not specified on the label which means one's pet would be using an unknown amount of drug daily. Obviously, if one is going to use a drug one should at the very least know how much is being used. As an alternative to Angel Eyes®, a precisely dosed capsule can be provided by a compounding pharmacy. Merit's product (Extra Strength Tear Stain Formula®) also lists its concentration of tylosin. The second controversy is whether or not it is even appropriate to use an antibiotic daily without a prescription for a cosmetic problem. Casual use of antibiotics is responsible for antibiotic resistance of bacteria in the environment and, in general, bacteria that become resistant to tylosin also become resistant to erythromycin. Since tear-staining is simply a cosmetic issue, perhaps non-antibiotic treatment could be used instead. For more details on this please visit the page on epiphora.

Tylosin can also be used in ferrets, rabbits, birds, reptiles, and pocket pets.


While there is definite side effect potential in large animal species, dogs in particular can tolerate very high doses of tylosin with no adverse effects. The biggest problem with small animal use seems to be the especially foul taste of tylosin which necessitates formulation into capsules, which is usually done by a compounding pharmacy.

Tylosin may falsely elevate certain liver blood tests (ALT and AST).


Tylosin can increase digoxin blood levels and should be used cautiously in patients taking digoxin for heart failure.

Page last updated: 5/27/2013