When a dog suddenly licks and scratches a specific spot again and again, the skin can become red, weeping and sore within a few hours. Many owners know it as a “hot spot”, but it can also be part of dermatitis—an inflammatory condition of the skin that can have several causes.

Light therapy with red, infrared and in some cases blue light is being used more and more as a gentle supplement to standard skin treatment. It is not a replacement for a veterinarian’s assessment, but it can be a useful tool to support healing, reduce inflammation and ease discomfort when used correctly.

What do “hot spots” and dermatitis actually cover?

A hot spot is also called acute moist dermatitis. It is typically a local area where the dog has irritated the skin by licking or scratching, after which heat, redness, oozing and pain develop quickly. The coat can become matted, and the skin can smell if bacterial overgrowth occurs.

Dermatitis is a broader term that includes everything from allergic skin inflammation to irritation from moisture, parasites or infection. Some dogs get small, recurring areas, while others get larger flare-ups on the belly, paws, ears or along the back.

An important point is that skin problems in dogs rarely come down to “just the skin”. Often there is an underlying cause that should be identified and managed—otherwise the problem returns.

Why can light affect the skin’s healing?

Light therapy for the skin is often called photobiomodulation. Specific wavelengths are used that can influence cellular activity without “burning” the tissue. With red and infrared light, cells absorb the light energy, among other places in the mitochondria where energy production takes place. The result can be increased ATP production, lower oxidative stress and signalling that supports repair.

In practice, it is associated with three things that are relevant for dog skin:

• reduced inflammation (redness, swelling, soreness)
• faster tissue repair (wound edges, granulation, collagen)
• pain relief (less discomfort can mean less licking and scratching)

That makes red and infrared light therapy interesting for hot spots, small wounds, irritated skin and as support for healing after procedures.

Red and infrared light: when the goal is calm, healing and less itching

Red light is typically around 630 to 660 nm, while infrared is often around 810 to 850 nm in devices used for home and clinical use. Red light works particularly well in the more superficial layers of the skin, while infrared penetrates deeper and is often used for pain, tension and inflammation in underlying tissue.

It is also worth knowing what red and infrared light do not do: They do not usually “sterilise” an area in the same way as antimicrobial treatment. If a hot spot is clearly infected, light can be supportive, but it does not remove the need for proper cleansing, possible antiseptic treatment and in some cases antibiotics, as assessed by the veterinarian.

Short coat provides better light penetration.

In practice, many protocols are in the range of a few minutes to 15 minutes per area, repeated daily for a short period for acute issues. For more stubborn cases, you can often work 3 to 5 times weekly for several weeks, depending on response and cause.

Blue light: targeted at bacteria, but requires care

Blue light (around 440 to 470 nm) has a more superficial effect in the skin and is mainly associated with antimicrobial effects. It can affect bacteria via photochemical reactions that bacteria are poor at handling.

At the same time, blue light is not “selective” in the way you always want. It can reduce bacteria broadly and can also affect the skin’s normal microbiome. Therefore, it makes the most sense for clearly infected or very superficial problem areas, preferably in collaboration with a veterinarian or following a clear plan.

In a veterinary context, treatments are also seen where blue LED light is used together with a gel that converts the light into fluorescence (often referred to as fluorescence biomodulation). Studies in dogs with bacterial skin infections suggest faster healing when light is included as a supplement to standard treatment.

Quick guide: when do you choose red/infrared, and when is blue relevant?

It helps to think in terms of “goals” before thinking in colours: Do you primarily want to reduce inflammation and support healing, or are there signs of infection that should be addressed more directly?

Here is a simple rule of thumb that often fits in practice:

The table cannot stand alone, but it makes it easier to choose a cautious starting point, especially for home treatment.

How to do it in practice for a small skin area

Always start by ensuring the problem is suitable for home care. If the skin is a deep open wound, bleeding heavily, very swollen, or the dog is clearly in severe pain, a veterinarian should assess it first.

When the area seems suitable, you can work systematically:

• Clean and prepare: Clip the coat short around the area so the light reaches the skin. Clean gently as recommended by the veterinarian and dry the skin carefully.
• Treat calmly: Position the light source steadily and at the correct distance (or in light contact if the device is designed for that). Keep the session so the dog can stay relaxed—ideally with treats or calm engagement.
• Repeat and evaluate: Use the same time each day for a short course, and assess progress based on redness, fluid, smell, warmth and the dog’s behaviour.

It is often better with regular, moderate sessions than a few very long ones.

Dosage: why time and intensity matter more than you think

In light therapy, “dose” is a product of intensity and time. Two devices can therefore produce very different results, even if they both emit red light. Many protocols in the literature for wounds and skin fall within a wide range (often around 1 to 10 J/cm² per area), and sessions can range from a few minutes to 10 to 15 minutes depending on the device’s output and treatment area.

If you use a handheld device with a small treatment field, you typically need to move it point by point. If you use a pad or a flexible light mat, you cover a larger area, but often with lower intensity per cm², which can mean a longer session time.

When adjusting a plan, it is often enough to change one thing at a time: either time per area or number of days per week. That makes it easier to see what the dog responds to.

Safety: what you must be uncompromising about

Light therapy is generally gentle, but there are some classic pitfalls. They mostly relate to eyes, heat and situations where you should hold back.

• Eyes: Light and laser must never be directed at eyes, and reflections from shiny surfaces must be avoided. Use protection according to the manufacturer’s instructions.
• Bleeding and fresh, open wounds: With active bleeding, you should wait and get an assessment, as increased blood flow may be undesirable.
• Pregnancy and growth plates: Treatment over a pregnant uterus is often discouraged, and in young animals you should be cautious around areas close to growth plates.
• Lumps and suspected tumour: Areas with unexplained lumps should be assessed before stimulating tissue.

Also watch for local heat. Dark skin and dense pigmentation can absorb more energy, so shorter sessions and breaks make good sense here.

What can you realistically expect with hot spots and dermatitis?

With a typical hot spot that is discovered early, red/infrared light therapy can often be used to reduce discomfort so the dog licks less, which in itself can give the skin some breathing room. Many find that redness and the “raw” surface gradually subside over a few days when the area is also kept clean and dry, and when the cause is addressed (fleas, moisture, stress, allergy).

With dermatitis where the cause is allergy, light can relieve symptoms, but it does not remove the allergy. Here, a good plan is often about combinations: skin barrier support, feeding, parasite control, possible medication and targeted care of flare-ups.

After a week of home care, there should be a clear direction. If it stays the same or gets worse, it is a sign that the cause requires more than local support.

Choosing equipment: LED, laser, treatment area and CE marking

For dog skin, you typically see two categories: LED-based devices and lasers. LED often covers larger areas and can be practical for areas such as the back, shoulder or larger skin patches. Laser can deliver high energy to a small area and is often used point by point.

When choosing equipment, it can be useful to look for:

• CE approval: An indication that the product meets relevant requirements for safety and documentation.
• Wavelengths: Red (approx. 630 to 660 nm) for skin and surface, infrared (approx. 810 to 850 nm) for deeper tissue and the pain component.
• Treatment area: Small hot spots can be handled with a handheld device, while larger areas are often easier with a pad or applicator.

Heat Sense is an example of a Danish provider that sells CE-approved devices for red and infrared light therapy for both home and professional use, delivered from stock in Denmark. Regardless of brand, it makes the most sense to choose equipment where the manufacturer clearly states wavelengths, output and recommended protocol.

When the veterinarian needs to be involved—even if you have light therapy at home

There are some skin scenarios where light therapy should only be a small part of the plan, or where you first need a diagnosis:

Infections that spread may require culture and targeted treatment. Repeated hot spots can be a sign of allergy, pain elsewhere in the body or parasites. Ear problems, paw problems and skin problems are often connected.

If you want to use light therapy wisely, it can be helpful to keep a simple log with date, area, duration and visible changes. That makes it easier to work with the veterinarian and adjust the effort without guessing.