If you're the owner of a Shih Tzu and you've had to deal with the hassle of tear stains, you may want to read this. The makers of two exported products and the manufacturer of Angels' Glow, Angels' Eyes, and Pet's Spark were presented with a letter of warning from the FDA. The reason for the letter was because these products were found to contain an unapproved antibiotic substance (tylosin tartrate) for the treatment of dogs or cats for tearstain-related conditions. If you're familiar with tear staining conditions, you may be familiar with these products, however, you may have been unaware of the fact that they are potentially dangerous.
The usual cause of tear staining is epiphora (a technical word used to explain the excess production of tears in dogs or cats). A tear stain is a reddish brown streak that is often found under the eyes of these pets. The Shih Tzu, the Maltese, and the Lhasa Apso are more vulnerable to this unusual condition. It is important that you see your veterinarian if your dog or cat happens to develop tear stains, as this can be a symptom of a serious eye health problem.
Tearstains occur as a result of porphyrin production. Porphyrins are waste products that occur from the breakdown of red blood cells in the animal body. These naturally occurring molecules leave the body just like other solid waste. They are excreted through urine, saliva and tears in dogs. Tearstains are more visible on a light-colored fur. As molecules that contain iron, porphyrins cause staining on the face of the animal and, as a result, last for a long period of time. Sometimes you may wonder why tearstains worsen when these pets go outside. This is because exposure to sunlight tends to darken the iron-containing stains.
However, you should note that not all stains that occur on your dog's face are caused by porphyrins. It is possible that your pet has developed a yeast infection on its face, especially if the stains are brown in color. Porphyrins are known to cause staining that is usually rust colored. So it is important that you are careful not to use a product intended for red stains to resolve brown stains or vice versa.
When a dog has a yeast infection, its face will begin to smell. This is a common feature with the infection. However, it is important to note that pets can also be infected with both a secondary yeast infection and a porphyrin stained face, especially from the constantly moist skin.
Typically, porphyrin infections are linked with genetics and innate bacterial levels since certain breeds of dogs are more vulnerable to staining. However, science has yet to ascertain why some dogs produce more porphyrin than others.