Dog Allergies and Sensitivities: Understanding the Root

The following is a guest post by Rita Hogan, a renowned herbalist and author of a new book, “The Herbal Dog.” She will be having a Q & A at The Big Bad Woof on Sunday 6/15. Tickets are free.

If your dog is constantly scratching, licking, developing ear infections, or reacting to more and more foods, you’re not alone. Many dogs today struggle with what dog owners call ”allergies.” But the truth is, most of these cases aren’t true allergies.  

A true allergy causes an immediate and severe immune response, like anaphylaxis. That reaction requires urgent veterinary attention, and an epinephrine shot to stabilize your dog’s body.  Anaphylaxis is a life-threatening medical condition!  

What most dog owners mean when they say “allergy” is “sensitivities”. These are immune system overreactions that build over time, triggered by underlying inflammation, poor digestion, and an overwhelmed detoxification system. In many cases, the root cause is organ system health.

The Role of the Liver and Lymphatic System

The liver and lymphatic systems are two often overlooked systems in dogs with sensitivities. When either one becomes stagnant or congested, it can contribute to immune overreactions, inflammation, and toxin buildup.

The liver filters waste, hormones, and digestion by-products. When sluggish, toxins and histamine can build up in the bloodstream, making your dog more reactive to foods, environmental triggers, and supplements. A backed-up liver can also impair digestion and nutrient absorption.

The lymphatic system is your dog’s internal drainage network. It helps clear cellular waste, remove toxins, and transport immune cells. When the lymphatic system is stagnant, the body can’t effectively remove waste or inflammation. This leads to poor skin health, fluid retention, and a slower recovery from allergic reactions.

A congested liver and a sluggish lymphatic system create a terrain (internal tissues) primed for sensitivities. Supporting both systems improves detoxification, immune balance, and resilience to triggers.

The Gut–Immune Connection

About 80% of your dog’s immune system lives in the gut. The immune system can’t function properly when digestion is compromised, whether from processed food, antibiotics, pesticides, chemical additives, or chronic stress. Proteins aren’t broken down entirely, toxins accumulate, and inflammation increases.

This overload makes your dog more likely to develop sensitivities to everyday foods, treats, trees, grasses, pollen, flea bites, candles, household cleaners, and more.

One of the most common patterns I see is leaky gut syndrome. This occurs when the intestinal lining becomes inflamed and permeable, allowing proteins, toxins, and bacteria to “leak” into the bloodstream. The immune system reacts, interpreting these substances as invaders, and the body launches an inflammatory response.

Over time, this constant immune activation exhausts the body’s defenses and creates widespread symptoms, including:

• “Allergies”
• Skin irritation and itching
• Chronic ear infections
• Loose stools or diarrhea
• Hot spots
• Gas, bloating, or reflux
• Behavioral changes (such as anxiety or irritability)
• New sensitivities to foods or supplements

Low Stomach Acid and Poor Digestion

Another hidden issue is low stomach acid. Dogs need strong stomach acid to break down proteins into amino acids, the building blocks of health. When proteins aren’t fully broken down, they are more likely to trigger immune reactions, create inflammation, and contribute to gut damage. Low stomach acid prevents this essential conversion and allows partially digested proteins to enter the small intestine, where they can become irritants instead of nourishment.

Many factors interfere with digestion:

• Antacids and acid blockers
• Antibiotics and NSAIDs
• Overcooked or processed food
• Vaccines and pharmaceuticals
• Fluoride, bromide, and chlorine
• Heavy metals and pesticides
• Low-quality kibble diets 

When the digestive system is disrupted, the immune system becomes confused. Instead of protecting the body, it reacts to normal substances like chicken, beef, pollen, or grass.

How do you restore balance? Start by simplifying the diet, supporting digestion, and using targeted herbs, mushrooms, and nutrients that help repair the gut and regulate the immune system.

Herbs, Mushrooms, and Supplements to Support Sensitive Dogs

You don’t need a hundred supplements to make a difference. The key is choosing the right tools based on your dog’s constitution, symptoms, and lifestyle.

Below are some herbs and fungi that have been successful in my practice with dogs.

Nettle (Urtica dioica, urens)
Nettle is a cooling herb that helps reduce inflammation, clear excess histamine, and support the kidneys and skin. It’s ideal for dogs with hot, red, itchy skin or seasonal reactions. Nettle also provides minerals, supports detoxification, and gently calms the immune response without suppressing it.

Dosage: Dried leaf: 1/8 teaspoon per 10 pounds of body weight, once daily.
Extract: 1 drop per 5-10 pounds, twice daily in food. Use dried nettle leaf or alcohol-free tincture.

Reishi Mushroom (Ganoderma lucidum)
Reishi is an adaptogenic mushroom that balances immune function, reduces allergic response, and supports liver detoxification. It also calms the nervous system, making it especially helpful for sensitive or anxious dogs.

Dosage: Powder: 1/8 teaspoon per 10 pounds of body weight, once daily with food. Tincture: 1 drop per 10 pounds, once or twice daily. Use a dual-extracted reishi powder or glycerine-based extract.

Lion’s Mane Mushroom (Hericium erinaceus)
Lion’s mane supports gut lining repair and helps restore digestive tract integrity. It’s especially effective for dogs with chronic gut inflammation, nervous system imbalances, or food sensitivities. 

Dosage:  Powder: 1/8 teaspoon per 5-10 pounds of body weight, once daily with food. Extract: 1 drop per 5 pounds of body weight, once or twice daily, mixed into food. Use a dual-extracted reishi powder or glycerine-based extract.

Tremella Mushroom (Tremella fuciformis)
Tremella is a hydrating mushroom that supports mucosal membrane health. It soothes the gut, supports moisture balance in the body, and aids in restoring healthy digestion.

Dosage: Powder: 1/8 teaspoon per 10 pounds, once daily. Extract: 1 drop per 5-10 pounds, once or twice daily. Use a dual-extracted reishi powder or glycerine-based extract.

Digestive Enzymes
Digestive enzymes are essential for dogs with food sensitivities, chronic skin issues, or poor digestion, and they’re necessary if your dog eats anything other than raw, fresh food.

Enzymes are naturally present in raw meat and unprocessed foods. Those enzymes are destroyed when food is cooked, extruded, or freeze-dried. That means your dog’s body has to work harder to break down proteins, fats, and carbohydrates. Over time, this stress contributes to inflammation, poor nutrient absorption, and immune confusion.

Dogs fed kibble, home-cooked meals, or freeze-dried food should always receive supplemental enzymes to support proper digestion and reduce the risk of food-related sensitivities. Even if the food seems high-quality, it’s still missing the enzymes your dog’s body needs to process it efficiently.

Look for a digestive enzyme blend that contains protease (for proteins), amylase (for carbohydrates), and lipase (for fats). You may also see papain or betaine HCL, which help break down tougher proteins and support stomach acid. 

Dosage: Follow the label based on your dog’s weight. Give with every meal of kibble, cooked, or freeze-dried food. Start low and increase gradually over 3 to 5 days.

Saccharomyces boulardii
Saccharomyces boulardii is a beneficial yeast that reduces inflammation, supports the gut lining, and helps re-establish healthy flora. It’s not a bacterial probiotic, so it’s safe to use even during infections or alongside antibiotics. Saccharomyces boulardii is an ideal short-term tool during elimination diets or gut repair protocols.

Dosage: Start with 1/4 capsule per 10 pounds of body weight daily, mixed with food. Increase slowly to full dose over 1 to 2 weeks. Use for 6 to 8 weeks, then reassess.

Apples (Malus spp.)
Apples are rich in quercetin, a natural antihistamine and antioxidant. They help calm inflammatory skin responses and support digestion. Peeled, raw, or gently cooked apples are cooling and generally well-tolerated.

Dosage: 1 to 2 slices for small dogs, up to 1/2 apple for large dogs, a few times per week. Avoid seeds and core.

Antihistamine Blend for Dogs

A natural antihistamine blend can make a real difference for dogs struggling with seasonal “allergies” or histamine overload. One effective combination includes nettle, maritime pine bark, and a food source of quercetin, like organic apple powder or dried rose hips.

Recipe: Natural Antihistamine Powder Blend

• 1 part powdered nettle leaf
• 1 part maritime pine bark powder
• 1 part organic apple powder or rose hips powder for extra vitamin C)

Mix ingredients thoroughly and store in an airtight jar.

Dosage: 1/8 teaspoon per 10 pounds of body weight, mixed with food twice daily during allergy season or times of flare-up.

This blend supports histamine regulation, liver detoxification, and reduces inflammatory skin reactions. It can be used alongside a simplified diet and other foundational supplements.

Sensitivities in dogs don’t happen or resolve overnight. When you understand the root cause of your dog’s condition, you can start to shift the terrain that created the problem in the first place.

By supporting digestion, strengthening the gut lining, and calming the immune system with herbs, mushrooms, whole foods, and foundational supplements, you help your dog build resilience.  This helps you move away from chasing symptoms and toward lasting wellness.