The telltale signs that your dog has fleas are often subtle at first, but they can quickly escalate into a full-blown infestation if left unchecked and untreated. Signs your dog has fleas include:

• Excessive scratching, biting, or licking: This is the most common symptom. Pay close attention to your dog’s behavior, especially around the base of the tail, belly, and inner thighs.
• Hair loss: In severe infestations, hair loss can occur due to constant scratching and biting.
• Skin irritation: Red, inflamed skin, especially around the flea bite areas, is a common sign. Small, raised bumps may also be visible.
• Hot spots: These are red, inflamed, and often oozing areas that are secondary bacterial infections caused by the dog’s scratching at flea bites. They can spread quickly if not treated.

And, sadly, finding one flea on your dog can indicate he is infested.

Can Fleas Kill a Dog?

While a few fleas are unlikely to seriously injure a dog, a severe flea infestation can lead to serious health problems, and in extreme cases, dogs can die from complications. Puppies, senior dogs, and dogs with weakened immune systems are particularly vulnerable to these complications.

Heavy infestations can cause anemia (low red blood cell count), which can be life-threatening. Flea bites can also cause intense itching and irritation, leading to excessive scratching and biting, which can damage the skin and make it vulnerable to secondary infections. Dogs can also ingest tapeworm larvae when grooming themselves and biting at fleas.

How to Spot Fleas and Signs of Fleas

Adult fleas are small, wingless insects, about 1 to 3 mm long, with a dark, flattened body. They move quickly and can be difficult to spot, but you may see them crawling through your dog’s fur, especially when parting the hair. Finding even one adult flea or its feces (often called “flea dirt”) is a sign of an infestation.

Similarly, never spotting a flea on your pet does not mean they don’t have fleas. It may seem odd that your dog has flea allergy dermatitis if you never see fleas. This is because your dog has an inherent ability to find, chase and subsequently eat the fleas, according to UC Davis School of Veterinary Medicine.

Telltale signs of fleas include:

Flea Dirt: Flea dirt, or flea feces, appears as small black specks and, when placed on wet paper, dissolves into reddish-brown streaks because it contains partially digested blood.

Flea Allergy Dermatitis: Flea allergy dermatitis is a common condition in dogs caused by an allergic reaction to flea saliva. Symptoms include intense itching, skin inflammation (redness, bumps, hot spots), hair loss, and secondary bacterial infections due to scratching.

Flea Bites: Flea bites on dogs appear as small, red, raised bumps, often clustered together. They are typically itchy, causing your dog to scratch excessively. The bites are usually most noticeable on the belly, groin, base of the tail, and inner thighs. The skin around the bites may become red, inflamed, and irritated. In some cases, secondary skin infections can develop due to scratching.

Is It Flea Season?

While fleas thrive in warmer weather, they can be a year-round problem for dog owners. Thanks to central heating and the resilience of the pupal stage of a flea’s lifecycle, the parasites can survive even in colder climates. They are often a year-round problem, especially in warmer climates.

Dr. Lindsay Starkey, of Auburn University, calls the notion of a specific flea season “a common misconception. Fleas and ticks can survive in winter. Pet and other animal owners need to protect their animals year-round.”

How Long Do Fleas Live?

The most common flea affecting dogs is ctenocephalides felis. The lifecycle of these consists of four stages: egg, larva, pupa, and adult. The entire process from egg to adult typically takes two to three weeks. The pupal stage is particularly important because the pupa is encased in a cocoon that protects it from environmental changes, allowing it to survive in carpets, furniture, and bedding for extended periods. This is a key factor in year-round flea infestations. Adult fleas represent only 1% to 5% of the total flea population at any given time. The remaining 95% are in the egg, larval, and pupal stages, hidden in the environment. This makes it important that you focus on killing fleas in your house, before they get to your dog.

Fleas vs. Ticks

While often mentioned together and often treated with one preventative prescription from your veterinarian, fleas and ticks look and behave differently.

Fleas are small, wingless insects that jump. Ticks are arachnids (related to spiders) that latch onto the skin and burrow their heads. Ticks are generally larger than fleas and do not jump. Fleas have a four-stage lifecycle (egg, larva, pupa, adult). Ticks also have a four-stage lifecycle of egg, larva, nymph, and adult. Unfed ticks are flattened and teardrop-shaped. Larval ticks have six legs, while nymph and adult ticks have eight legs.