A hot spot is most commonly a raw, inflamed skin lesion on a dog that appears suddenly and spreads fast. The term also has distinct meanings in geology, ecology, and public health. If you searched “what is a hot spot,” you’re likely dealing with one of these contexts, so here’s what each one means and why it matters.
Hot Spots on Dogs
In veterinary medicine, a hot spot (formally called pyotraumatic dermatitis or acute moist dermatitis) is a red, moist, oozing patch of inflamed skin that can appear on a dog within hours. These lesions are warm to the touch, often painful, and may contain pus. They show up most frequently on the head, legs, and hips, though they can develop anywhere on the body.
What makes hot spots alarming is their speed. You might notice a tiny red spot in the morning and come home to find a raw lesion the size of a pancake. That rapid expansion is driven by a self-reinforcing cycle: something irritates the skin, the dog licks or scratches it, the trauma creates more irritation, and the dog keeps licking. This lick-itch-lick cycle is the engine behind every hot spot.
Common Triggers
Hot spots rarely appear out of nowhere. The most common underlying causes are allergies and flea bites, both of which create the initial itch that kicks off the cycle. Ear infections are another frequent culprit, particularly in dogs that swim. Wet ears that don’t dry fully can trigger infection and irritation under the ear flap, which quickly turns into a hot spot.
Moisture in general is a major risk factor. Dogs with thick coats that swim, wade, or even get caught in a warm rain are especially vulnerable if their fur doesn’t dry completely. Matted areas trap moisture against the skin, creating the perfect environment for bacterial growth and sores. Breeds with dense double coats tend to be more susceptible for exactly this reason.
How Hot Spots Are Treated
The first step is clipping the fur around the lesion so air can reach the skin and topical treatments can make contact. This alone can make a significant difference, since trapped moisture and matted fur are what keep the infection going.
Topical antiseptic treatment, typically a chlorhexidine-based solution applied once or twice daily for about seven days, is the standard approach. International veterinary guidelines recommend topical antiseptics over oral antibiotics for hot spots, since the infection sits right on the skin’s surface and responds just as well to direct treatment. Oral antibiotics are generally unnecessary and best avoided for this type of surface-level infection.
Because itching and pain drive the self-trauma cycle, reducing inflammation is just as important as fighting the infection. A vet may prescribe a short course of anti-inflammatory medication, usually five to seven days, to break the itch cycle and let the skin heal. An e-collar (the “cone of shame”) often plays a role too, physically preventing the dog from reaching the area.
Preventing Recurrence
Hot spots tend to come back if the underlying trigger isn’t addressed. If fleas are the issue, consistent parasite prevention is essential. For dogs with environmental or food allergies, working with a vet to identify and manage the allergy is the longer-term fix. Dogs that swim regularly should be towel-dried thoroughly afterward, with special attention to the ears and any areas where fur is dense or prone to matting. Regular grooming and keeping the coat free of mats reduces the risk substantially.
Geological Hotspots
In geology, a hotspot is an area where a plume of unusually hot material rises from deep within the Earth’s mantle, melting through the crust above to form volcanoes. The Hawaiian Islands are the most famous example. Unlike volcanoes that form at the edges of tectonic plates, hotspot volcanoes can appear in the middle of a plate.
The key feature of geological hotspots is that the mantle plume stays relatively stationary while the tectonic plate above it keeps moving. This creates a chain of volcanoes over millions of years. The youngest, most active volcano sits directly over the plume, while progressively older, extinct volcanoes stretch out in a line behind it, carried away by plate motion. Eventually those older volcanoes erode, sink below the waterline, and become seamounts. Scientists use the direction and age progression of these volcanic chains to reconstruct the history of how tectonic plates have moved over time.
Biodiversity Hotspots
In conservation biology, a biodiversity hotspot is a region that contains an exceptionally high number of species found nowhere else on Earth while simultaneously facing severe habitat loss. The concept was formalized around the year 2000 using data primarily from flowering plants, defining hotspots as places where high endemism (species unique to that area) and high threat intersect. Conservation organizations use these designations to prioritize where limited funding and resources will have the greatest impact. There are currently 36 recognized biodiversity hotspots worldwide, including Madagascar, the Atlantic Forest of Brazil, and the mountains of Southwest China.
Disease Hotspots in Public Health
Epidemiologists use “hotspot” to describe a geographic area where a disease is spreading at a significantly higher rate than surrounding areas. The CDC and other agencies identify these clusters using spatial analysis software that compares infection rates at specific locations against the overall expected rate for a region. When a facility or neighborhood shows a statistically significant spike, it’s flagged as a transmission hotspot, which helps public health teams concentrate testing, treatment, and prevention resources where they’re needed most.