Side Effects of Benadryl in Dogs

Benadryl, also known by its generic name diphenhydramine, is a common over-the-counter medication used in humans to treat allergies, insomnia, and motion sickness. Due to its sedative and anti-allergic properties, it is also frequently administered to dogs. While Benadryl is generally considered safe for pets when used responsibly, it is crucial to understand the potential side effects and proper dosage to ensure your furry friend’s safety.

Key Takeaways:

  • Common Side Effects: Sleepiness, dry mouth, and urinary retention are the most frequently observed side effects. These are generally mild and tend to resolve on their own.
  • Rare Side Effects: Gastrointestinal issues such as diarrhea and vomiting, as well as loss of appetite, are less common but can occur.
  • Serious Side Effects: Increased heart rate, rapid breathing, disorientation, and seizures are rare but serious side effects that require immediate veterinary attention.

Understanding Benadryl and Its Uses in Dogs

Diphenhydramine belongs to a class of drugs known as antihistamines, which work by blocking the effects of histamine, a substance in the body that causes allergic symptoms. When dogs come into contact with allergens, their bodies produce histamine, leading to symptoms such as itching, swelling, and other discomforts. Benadryl can help alleviate these symptoms, making it a go-to option for pet owners.

Potential Side Effects of Benadryl in Dogs

Like all medications, Benadryl can cause side effects. The severity and occurrence of these side effects can vary based on the dog’s age, breed, health status, and dosage received. Below is a detailed table chart outlining potential side effects and their frequency:

Side Effect Common Rare Serious
Sleepiness ✔️
Dry Mouth ✔️
Urinary Retention ✔️
Diarrhea ✔️
Vomiting ✔️
Loss of Appetite ✔️
Increased Heart Rate ✔️
Rapid Breathing ✔️
Disorientation ✔️
Seizures ✔️

Dosage: Finding the Right Balance

The correct dosage of Benadryl for dogs is imperative to prevent overdosing. A common guideline is 1 mg of Benadryl per pound of body weight, administered 2-3 times a day. However, this can vary based on the dog’s specific needs and health status. Always consult with a veterinarian before administering Benadryl to ensure the proper dosage.

Alternatives to Benadryl

1. Cetirizine (Zyrtec)

Cetirizine, commonly known as Zyrtec, is another antihistamine that has gained popularity for use in dogs due to its effectiveness in managing allergy symptoms with a lower sedative effect compared to Benadryl. It works by blocking histamine receptors, preventing the allergy symptoms from escalating. The typical dosage is around 0.5 mg per pound of body weight, once daily. However, pet owners should be cautious and opt for formulations that do not contain additional decongestants, as these can be harmful to dogs.

2. Fexofenadine (Allegra)

Fexofenadine, also known as Allegra, is praised for its non-sedative properties, making it a suitable option for pets where drowsiness is a concern. It operates by hindering histamine-induced reactions, offering relief from allergic symptoms. The standard dosage lies around 1-2 mg per pound of body weight, administered once daily. Ensuring that the product is free from pseudoephedrine is crucial, as this decongestant can be toxic to dogs.

3. Loratadine (Claritin)

Loratadine, or Claritin, is another non-sedating antihistamine option. It works by selectively blocking peripheral histamine receptors, effectively reducing allergy symptoms without causing significant drowsiness. The recommended dosage is generally 0.12-0.22 mg per pound of body weight, given once a day. Pet owners should be vigilant in selecting a product that is free from additional ingredients like decongestants.

4. Oclacitinib (Apoquel)

Oclacitinib, commercially known as Apoquel, operates differently from traditional antihistamines. It targets cytokines involved in the itching process, providing rapid relief from allergic itch without many of the side effects associated with steroids. The dosage is dependent on the dog’s weight, and it requires a veterinary prescription. Apoquel is highly effective but may be costlier than over-the-counter antihistamines.

5. Omega-3 Fatty Acids

Integrating Omega-3 fatty acids into your dog’s diet can help manage allergies by reducing inflammation in the body. Fish oil is a common source of Omega-3s, and it can be added to your dog’s food in liquid or capsule form. The dosage depends on the dog’s size and the product’s concentration, and it may take several weeks to notice a significant improvement.

6. Topical Solutions and Shampoos

For localized allergic reactions, such as hot spots or itchy skin, topical solutions and medicated shampoos can provide direct relief. Products containing hydrocortisone can help alleviate itching, while shampoos with oatmeal and aloe vera can soothe irritated skin.

7. Immunotherapy

For chronic or severe allergies, immunotherapy, also known as allergy shots, may be an option. This long-term treatment involves administering small amounts of the allergen to the dog over time, with the goal of building tolerance and reducing allergic reactions. This approach requires a substantial commitment but has the potential to address the root cause of the allergies.


What are the bad side effects of Benadryl in dogs?

Serious side effects such as increased heart rate, rapid breathing, disorientation, and seizures are considered severe and require immediate veterinary attention.

How does Benadryl make my dog feel?

Benadryl typically makes dogs feel sleepy and may cause them to be more sedate than usual. This is due to the medication’s sedative properties.

Why shouldn’t I give my dog Benadryl?

Avoid giving your dog Benadryl if they have a known allergy to the medication, are pregnant or nursing, have glaucoma, or are suffering from certain medical conditions such as heart disease or high blood pressure. Always consult with a veterinarian before administration.

How Much Benadryl Can I Give My 50 lb Dog?

For a 50 lb dog, the typical dosage of Benadryl would be around 50 mg every 8 hours. However, this is a generalized guideline, and individual dog needs can vary significantly. It’s always a safer practice to get a precise dosage tailored to your dog’s specific condition and overall health by consulting with a veterinarian.

How Often Can I Give My Dog Benadryl for Itching?

Benadryl is commonly used to alleviate itching in dogs, and it’s generally safe to administer it 2-3 times a day. The exact frequency and dosage, though, should be determined based on the underlying cause of the itching and your dog’s overall health condition. Extended use without veterinary supervision is not recommended.

Can Benadryl Cause Any Long-term Effects in Dogs?

While short-term use of Benadryl is generally safe for dogs, long-term use could potentially lead to some issues. These may include an increased tolerance to the medication, reducing its effectiveness, and the possibility of side effects like urinary retention becoming more prominent. Any long-term medication regimen should be closely monitored by a veterinarian.

Is Benadryl Safe for All Dog Breeds?

Most dog breeds tolerate Benadryl well, but some breeds are more susceptible to its sedative effects. Additionally, brachycephalic breeds (those with short noses and flat faces, such as Bulldogs and Pugs) may be more prone to respiratory issues, which can be exacerbated by Benadryl’s side effects. Consulting with a vet before administering Benadryl to these breeds is crucial.

Are There Any Specific Conditions That Make Benadryl Unsafe for My Dog?

Dogs with certain health conditions should avoid Benadryl. These conditions include glaucoma, high blood pressure, cardiovascular disease, and urinary retention issues. Additionally, dogs that are pregnant or nursing should not be given Benadryl without consulting a veterinarian.

Can I Use Benadryl Cream on My Dog’s Skin?

While Benadryl tablets are commonly used for allergies and itching, using Benadryl cream on a dog’s skin is not recommended. Dogs are likely to lick the area, ingesting the cream, which can lead to toxicity. There are safer alternatives specifically designed for topical use on dogs that a veterinarian can recommend.

What are the Signs of Benadryl Overdose in Dogs?

Signs of Benadryl overdose in dogs include extreme lethargy, uncoordinated walking, dilated pupils, rapid heartbeat, and agitation. In severe cases, it could lead to seizures and respiratory failure. If you suspect your dog has ingested an overdose of Benadryl, seek immediate veterinary attention.

What Alternatives to Benadryl are Available for Dogs with Allergies?

There are various alternatives to Benadryl for treating allergies in dogs. These include other types of antihistamines like cetirizine, as well as prescription medications like Apoquel and Cytopoint. Additionally, omega-3 fatty acid supplements can support skin health and reduce allergic reactions. A vet can provide guidance on the best choice for your dog’s specific needs.

Can I Give My Dog Benadryl for Anxiety or Motion Sickness?

Benadryl has sedative properties and can be used to help alleviate anxiety and motion sickness in some dogs. However, it’s not a one-size-fits-all solution, and not all dogs will respond the same way. There are also specifically designed medications and therapies for these issues, which might be more effective and safer in the long run.

What Should I Do If My Dog Reacts Adversely to Benadryl?

If you notice any adverse reactions or side effects after your dog has taken Benadryl, it’s crucial to contact your veterinarian immediately. They can advise on whether the symptoms are serious enough to require immediate medical attention or if they can be managed at home. Your vet might also decide to alter the dosage or recommend a different medication altogether.

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