Frontline Plus Side Effects With Aged Dogs

Written by angela brady
  • Share
  • Tweet
  • Share
  • Pin
  • Email
Frontline Plus Side Effects With Aged Dogs
Older dogs can have an increased sensitivity to many flea-control products. (dog image by Trav from

Frontline Plus is a topical antiparasitic medication used to kill and prevent fleas and ticks. The main ingredient is fipronil, which works by disabling the central nervous system of the parasites, causing death. Fipronil is not absorbed into the bloodstream, but it is applied to a small area of skin between the dog's shoulder blades and remains chemically bound in the hair and skin oils. Although generally safe, Frontline Plus and other fipronil-based products are not recommended for use with geriatric dogs. Dogs are considered geriatric after seven years of age.

Skin Sensitivity

The most common side effect of Frontline Plus in geriatric dogs is an itchy rash at the application site. As dogs age, their skin thins and can become more sensitive to chemicals and environmental factors. When the Frontline Plus is applied, the chemical can irritate the skin, causing itchiness. When the dog scratches, the thin, dry skin can easily abrade, allowing the chemical to penetrate the skin. This causes more itching, so the dog scratches, and the rash cycle begins. The area will turn red, and bumps or welts may appear.

Insufficient Distribution

Topical flea and tick medications rely on the skin's natural oils to distribute the medication around the body. The heat of the dog's body allows the medication to mix with the skin's oils, and the dog's movement helps the oil to spread out and eventually cover the entire body. Older dogs are more likely to have thinning hair and drier skin, and consequently a less effective mechanism for distributing the medication. The result is that the bulk of the medication stays at the application site for an extended period of time and can cause burning and irritation. Occasionally, skin discolouration and hair loss can occur at the application site.

Inaccurate Dosing

Frontline Plus is dosed according to weight. In a young, healthy dog, the body weight is made up of a certain percentage of bone, muscle, fat, and organs, depending upon the breed. All of these different body components process chemicals differently. As a dog gets older he begins to lose muscle mass, which affects the way his body metabolises chemicals. A dose that would not affect a younger dog of the same weight could cause problems for the older dog. If the Frontline Plus were to somehow enter the bloodstream (most commonly if the dog licks a fresh application site), it could have negative effects on bodily systems.

Fipronil Allergy

Older dogs can sometimes develop allergies to certain foods or medications they have been repeatedly exposed to throughout their lives. Although rare, an allergy to fipronil can have serious consequences in older dogs, especially if they already have an underlying chronic condition. Most allergic reactions occur within a few minutes of applying the second dose of Frontline Plus, but if the dog has been exposed to fipronil before, it could happen on the first dose. Symptoms of an allergic reaction include increased salivation, vomiting, diarrhoea, depression, and nervousness.


If signs of irritation are seen at the application site, flush with cold water to wash off as much product as possible, then consult a veterinarian. If nervousness, vomiting, diarrhoea, or any other systemic symptoms occur, see a veterinarian immediately because the condition could potentially be life-threatening.

Don't Miss

  • All types
  • Articles
  • Slideshows
  • Videos
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the site, you consent to the use of cookies. For more information, please see our Cookie policy.