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What are Skin Reaction to Allergies?

Allergic reactions for dogs often appear on the skin as of redness, swelling, and itching. There are several forms these skin reactions can take, including granulomas, angioedema, and urticaria. Although the skin-related effects of allergies are not generally life-threatening, they can develop into more serious problems. The wheals, pustules, and other bumps associated with allergic responses can become particularly itchy, and many dogs will scratch at them until they become even more inflamed or even rupture which can lead to dangerous skin infections. 

Dogs can be affected by a number of different allergies, and most of them take the form of uncomfortable, itchy skin conditions that can sometimes rupture and become infected if left untreated.

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Symptoms of Skin Reaction to Allergies in Dogs

Skin reactions to allergies can take many forms, and although the size, composition, and location of any bumps or wounds may vary, depending on the type of reaction that is experienced. Symptoms which point to an allergy might include:

  • Abrasions (usually from scratching) 
  • Affected skin is warmer than usual
  • Excessive licking or chewing, particularly on feet and joints
  • Hair loss
  • Increased itching
  • Raised bumps
  • Reddened skin
  • Swollen skin
  • Ulcerations


Acral lick granuloma is a granulomatous disorder of the skin that is either caused or worsened when a canine compulsively licks a particular spot on their body until a granuloma develops. Although this is not strictly an allergic condition, it is often triggered by allergic itching.

Angioedema is a subcutaneous reaction, often caused by an allergy, that produces red, raised bumps deep in the fatty layer under the skin. The bumps also produce swelling and discomfort in the surrounding tissues.

Atopy is another allergic skin reaction characterized by inflammation and intense itching. Dogs with atopy also tend to develop papules, which are tiny raised bumps, usually under a centimeter in diameter.   

Urticaria is a common skin reaction to allergens known more commonly as hives distinguished by red, raised bumps that cause intense itching.

Causes of Skin Reaction to Allergies in Dogs

Allergies in canines are due to the inappropriately aggressive response of specialized cells to the allergen. These cells, known as mast cells are tasked with the job of protecting the body from pathogens. When the immune system is activated by a particular substance, it manufactures its own protein which causes the mast cells to release histamine. Histamine is a naturally occurring compound that has an inflammatory effect on the tissues that it comes into contact with including skin, which results in the itchy and inflamed skin conditions characteristic of an allergic reaction in canines.

Diagnosis of Skin Reaction to Allergies in Dogs

Allergies are the most frequent cause of these types of skin disorders, but not the only possibility.  Skin scrapings will often be collected from any areas that are affected by bumps or rashes, to be utilized in the microscopic examination of the skin cells known as a cutaneous cytology to look for issues like signs of bacterial or fungal infections or infestations by parasites such as mites or fleas. The veterinarian is also likely to request a biochemistry profile and a complete blood count to check for disorders such as a systemic infection or even hormonal imbalances which can cause similar symptoms. These blood tests may also expose an overabundance of a variety of white blood cells known as eosinophils that often signifies that a recent allergic reaction has taken place. Once any alternatives have been eliminated an allergy will be suspected, and the emphasis will be placed on determining which allergen is causing the reaction.

Allergies of all sorts can cause skin reactions in canines; this can include not only contact allergies, but also food allergies, drug allergies, and environmental allergies like allergies to pollen. Several types of allergy may be defined using intradermal testing, in which small amounts of the suspected allergen or allergens will be injected under the skin to identify which allergen is affecting the patient. Intradermal testing is generally unreliable for allergies to food, so dietary trials are considered the gold-standard method of uncovering which ingredient the canine is reacting to.

Treatment of Skin Reaction to Allergies in Dogs

If your dog has developed an allergic reaction, your veterinarian will give you instructions on how to ease the dermal itching and swelling. Quite often reactions like urticaria or angioedema disappear spontaneously, but in cases where these reactions persist, antihistamine medications such as Benadryl or Zyrtec are often the first line of defense employed in order to combat allergic reactions. Antihistamines are only effective for an estimated 20% - 30% of allergic dogs, and even those effects can fade with time. There are also many natural remedies that are quite effective in easing the itching sensations that are common to most allergic skin reactions. Oatmeal ground into flour, also known as colloidal oatmeal, is a safe and inexpensive treatment which can be found in many pantries, and some essential oils such as peppermint, lavender, and chamomile can help relieve the itching and pain that are typically associated with allergies that affect the skin.

A veterinary professional should also be consulted before administering any over-the-counter medications to your dog, as there can be a large dosage differences for canines that are based not only on the weight of your dog but also on their overall physical condition and concurrent medications and supplements they may be taking. When natural remedies and antihistamines fail to control the symptoms, steroids and corticosteroids may be employed, although side effects should be taken into account, especially when used as a long-term solution.

Recovery of Skin Reaction to Allergies in Dogs

In most cases, allergic reactions tend to get more aggressive with repeated exposures to the allergen. Veterinary professionals will often prescribe an epipen if your dog has had a moderate to severe allergic reaction, as indicated by skin reactions such as hives or angioedema. This device has a properly measured dose of epinephrine for your canine, to be employed if the animal experiences an anaphylactic reaction.

Dogs that are over 45 pounds are typically prescribed a regular adult sized EpiPen, whereas dogs that are between 20-45 pounds will use the EpiPenJr, and animals that weigh less than 20 pounds are usually given a syringe with the proper dose for their particular size. Use of an EpiPen should be immediately followed by a trip to the emergency room, even if your dog appears fully recovered. Epinephrine is a short-acting drug, and the allergic reaction may resume without proper medical treatment.

Skin Reaction to Allergies Questions and Advice from Veterinary Professionals

Frenchie Mix
1 Year
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Itching, redness, scabbing

Medication Used

Purina Calming Care

My dog recently developed red inflammation around her shoulders, an armpit, belly, and is developing a hotspot under her chin. She’s on a limited ingredient hypoallergenic diet and has developed irritations from scratching before, but not to this degree. I shaved under her chin and am using a topical cream from the vet from when she had a hotspot months ago, but I’m concerned about pinpointing the cause. She mostly scratches in her crate, and she does get warm in the affected areas after laying down for long periods. I’ve read the heat could be an indication of overactive yeast on the skin. She just had a bath and I haven’t changed laundry detergent. Any guidance or ideas?

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Labrador Retriever
1 Year
Moderate condition
0 found helpful
Moderate condition

Has Symptoms


My 1 year old lab had an allergic reaction to antibiotics and the skin ulcers have healed but he is left with blotches all over his body and the hair isn't growing back. How can I help him to get the hair back and return his coat back to where it was before??

Dr. Michele King, DVM
Dr. Michele King, DVM
1611 Recommendations
If Jackson had ulcers from the reaction, that hair should grow back over time. It can take 2-3 months for hair to fully recover from an insult, and you should notice the patches returning over that time frame. If they are not, it may be a good idea to have his skin looked at by a veterinarian to make sure that there isn't anything else going on.

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