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What is Antihistamines Poisoning?

Antihistamines can be found in over-the-counter cold, allergy, and sinus medications. Antihistamines are used by humans to treat a variety of conditions, such as allergies and sinus ailments. Antihistamines may also contain combination ingredients, such as aspirin, codeine, caffeine, dextromethorphan, and pseudoephedrine. Common brands of antihistamines include Dimetane, Zyrtec, Chlor-Trimeton, Tavist, Benadryl, Allegra, and Claritin. If a dog has ingested antihistamines, it will be very important to take the box that contained the medication with you to the veterinarian so the ingredients will be known.

Antihistamines come into categories: first-generation and second-generation. First-generation antihistamines, when taken, have a sedative effect. Many people refer to these as the “older” antihistamines since they can cause marked drowsiness, unlike the second-generation medications. They can also cause blurry vision, dry mouth, difficulty with coordination and concentration, and nausea. The second-generation antihistamines are purchased more often since they are in non-drowsy form; however, if they are taken above the recommended dosage they can still have the same side-effects as first-generation antihistamines.

Antihistamines poisoning in dogs occurs when dogs ingest a quantity of medications, either over-the-counter or prescription, that contain antihistamines. This type of toxicity is treatable if immediate medical attention is given.

Antihistamines Poisoning Average Cost

From 33 quotes ranging from $200 - $1,000

Average Cost

$350

Symptoms of Antihistamines Poisoning in Dogs

When dogs overdose on antihistamines, symptoms depend on the quantity consumed. Symptoms of antihistamine poisoning in dogs include:

  • Rapid heartbeat
  • Irregular heartbeat
  • Hyperactivity
  • Seizures
  • Vomiting
  • Confusion

Types

It is important to know the type of antihistamine your dog ingested and the ingredients contained in combination with the particular medication. Differential diagnoses of antihistamine poisoning in dogs include:

  • Amphetamine poisoning
  • Caffeine poisoning
  • Pseudoephedrine overdose
  • Alcohol toxicity
  • Marijuana toxicity
  • Barbiturates or tranquilizer overdose
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Causes of Antihistamines Poisoning in Dogs

When a dog consumes antihistamines, depending on the amount ingested, toxicity can occur. Poisoning due to antihistamine overdose is caused by:

  • The constriction of the smooth muscles in the respiratory tract
  • The increased permeability of the capillaries
  • Negatively affects the central nervous system
  • Cardiovascular abnormalities
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Diagnosis of Antihistamines Poisoning in Dogs

Once you have taken your dog to the veterinarian, he will need to know more information about what the dog ingested. This is why bringing in the box or container of the medication is very helpful. The veterinarian will perform specific laboratory tests, namely blood testing, plasma tests, and evaluations to check the dog’s concentration of serum antihistamine. The veterinarian will also perform urinalysis and possibly a biochemistry profile in order to check the levels of antihistamines in the dog’s system. If the veterinarian is certain that the dog has ingested antihistamines, due to the evidence of the box and your observations of his past consumption, he may rely heavily on his clinical signs in order to determine the mode of treatment.

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Treatment of Antihistamines Poisoning in Dogs

Once the veterinarian has made a diagnosis of antihistamine poisoning, he will immediately begin treatment. Treatment methods include:

Emesis

If your dog has already vomited, the veterinarian will not need to induce vomiting. The induction of vomiting may be conducted in order to help rid the dog of the substance. Once emesis has occurred, the dog should display natural gastrointestinal decontamination, or the veterinarian will give the dog activated charcoal to aid in the absorption of any residual toxic substances.

Medications

Medications to suppress the central nervous system may be given, especially if the dog is having seizures. Diazepam is often the drug of choice to control any seizure activity, and there are other drugs that work as well. Medications, namely methocarbamol, guaifenesin, or pentobarbital may also be used.

Monitoring of Systems

The veterinarian will closely monitor the dog’s heart rate, arrhythmia, and respiratory rate. The monitoring of systems also is dependent upon if the animal ingested a medication that has been combined with the antihistamine.

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Recovery of Antihistamines Poisoning in Dogs

The prognosis for antihistamines poisoning in dogs is good if treated promptly. Once the dog has shown progression after treatment and recovery, the veterinarian will give you detailed instructions on how to continue to care for your dog at home. Monitoring your dog after treatment is very important; your veterinarian will want to see him again to check his vitals and to be sure that he is recovering properly. Before you take him to the veterinarian for a follow-up visit, if you see any changes in his behavior for any new symptoms it is imperative to contact your veterinarian. In order to prevent antihistamines poisoning in dogs, it is crucial to store all medications in a safe place that is not accessible by the dog for any other pets. Many dog owners choose to store the medications in a box with a lid to further prevent any accidental ingestion.

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Antihistamines Poisoning Average Cost

From 33 quotes ranging from $200 - $1,000

Average Cost

$350

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Antihistamines Poisoning Questions and Advice from Veterinary Professionals

Need pet health advice? Ask a vet

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Ask a Vet

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Husky

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Seven Years

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Unknown severity

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0 found helpful

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Unknown severity

Has Symptoms

None

my dog got into a bottle of children's benadryl

Sept. 15, 2020

Owner

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Jessica N. DVM

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0 Recommendations

Hello- If the only ingredient is diphenhydramine, and there is not xylitol used as a sugar substitute your pet should not have any problems except mild sedation. If there are other active ingredients besides diphenhydramine or xylitol is on the ingredient list then I would recommend calling pet poison control. Xylitol is very toxic to dogs.

Sept. 15, 2020

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Hovawart mix

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5 1/2 months

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Unknown severity

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1 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Unknown severity

Has Symptoms

None

My puppy chewed on my eye drop bottle. They are an antihistamine eye drop. Ketotifen fumarate ophthalmic solution 0.035% is the active ingredient. It was a new 0.17oz bottle. It appears that the majority of it leaked all over the sheets and mattress so I'm not sure how much she actually got. She is about 5 1/2 months old and 30 pounds. It happened a little under an hour ago and she has no symptoms.

Aug. 1, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. I don't have any information on whether that medication will be a problem or not, unfortunately. It would be best to call a Pet Poison Control hotline, as they have databases on different medications and any effects. They will be able to help guide you as to what you need to do for her. 888-426-4435. I hope that all goes well for her!

Aug. 1, 2020

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Cavapoo

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Five Years

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Unknown severity

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0 found helpful

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Unknown severity

Has Symptoms

None

Dog may have eaten one allegra 60 mg pill. He is aboutb19 pounds

Aug. 1, 2020

Owner

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0 Recommendations

Allegra (fexofenadine) is a medicine which is used in veterinary medicine and a 60mg pill would be just over a therapeutic dose (1-2.5mg/lb) for a 19lb dog. However, Allegra D contains pseudoephedrine which can be dangerous for dogs; if your dog consumed an Allegra D pill, I would recommend visiting your veterinarian especially if symptoms of hyperactivity, panting and rapid heart rate develop. https://www.avma.org/javma-news/2005-02-15/pseudoephedrine-alert-issued#:~:text=As%20little%20as%20one%20tablet,size%20dog%20can%20be%20lethal.

Aug. 1, 2020

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Havanse

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10 months

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Unknown severity

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None

I’m not sure if my dog ate an allergy relief d. I have try to induce vomiting but it didn’t work. What else should I be watching for

July 25, 2020

Owner

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Dr. Michele K. DVM

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Thank you for your question Without knowing the weight of your dog or the strength or brand of the tablet, I can't say whether your pup will have a problem or not, unfortunately. You can either call your closest emergency clinic and give them that information, or a Pet Poison Control Hotline, and they will be able to give you more information once they know those details. I hope your pup is okay.

July 25, 2020

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Havanese

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Seven Years

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Unknown severity

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0 found helpful

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Unknown severity

Has Symptoms

Sneezing

How much can I give her if it’s children’s loratadine/Claritin and is it safe she’s 5pound

July 19, 2020

Owner

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Dr. Gina U. DVM

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0 Recommendations

Hello I'm so sorry that your pet is sneezing. Unfortunately I cannot give medication dosage advice over this platform. I recommend that you call your veterinarian that has seen your pet for this information. Good luck.

July 19, 2020

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Suebie

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Pit bull

dog-age-icon

3 Years

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Serious severity

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Serious severity

Has Symptoms

Panting
Nervous
Anxiety

My pit mix was overdosed. She was given 1 full pill yesterday and 1 full pill today if Claritin -D Walmart brand. It’s non drowsy allergy and congestion relief-d. With pseudoephedrine 240mg and Loratadine 10mg. I got The wrong pills. Since she had been given the wrong dosage and possible the wrong pills, I’m worried. She has a different demeanor, she is panting but not active, she won’t drink water, ears are back as if she’s anxious and her pupils are huge. It’s like she’s high. No vomit or seizures. She is a Pit Mix at 72-78 pounds.

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Steve

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Chihuahua

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11 Years

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Fair severity

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Fair severity

Has Symptoms

None

My approx 13.5 lb chihuahua was accidentaly given a single 10mg certrizine dose instead of a 5mg. I have read the certrizine dose is 0.5 mg per pound but benadryl is 1mg per pound. He seems perfectly fine at the moment and isn't exhibiting any symptoms but I am concerned that as time passes he will. Should I induce vomiting to get it out?

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Duncan

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mini schnauzer

dog-age-icon

9 Years

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Fair severity

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pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Fair severity

Has Symptoms

Loose Bowel Movements

My dog ate approx 2 or 3 tabs of claritan. not sure when. hes 20 lb schnauzer. 9 yrs old. only symptom has been loose stool. He seems fine other than the stool He has had 2 loose movements in a 10 hr time span.

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dixie

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Jack Russell Terrier

dog-age-icon

9 Years

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Fair severity

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pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Fair severity

Has Symptoms

my 21 lb jack russell ate 180 mg allegra at 7am. it is 2 pm and she appears to be fine. do I need to do anything? I did not think it would harm her. now after reading this article I am concerned. What should I do?

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Mojo

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Shih Tzu

dog-age-icon

6 Years

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Mild severity

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pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Mild severity

Has Symptoms

Confused

Shitzu 14lb gave her 2.5mg of Claritin non drowsy allergy and sinus tablet. No problem last night but tonight she is just staring at the floor and seems confused. Should I be concerned?

Antihistamines Poisoning Average Cost

From 33 quotes ranging from $200 - $1,000

Average Cost

$350