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Chihuahua Allergies and Benadryl

Please Note:

This site offers general information and is not meant to take the place of professional medical advice for your puppy or dog. You should always check with your Chihuahua's veterinarian before deciding on a treatment option for your pet.


You may be wondering if it is okay to give Benadryl to a Chihuahua puppy or dog and if so, how much should you give him or her. It is generally safe to give it to a Chihuahua; however it is also important to follow safe guidelines and correct dosing is important. 

You can learn all about the option of this here, however should check with your dog's vet before giving any to him or her.

Benadryl is the brand name of the allergy medication called diphenhydramine. It is a fast acting antihistamine that can quickly treat allergic reactions.

When a dog (or a person) encounters an allergic trigger, the body releases histamine which then produces typical symptoms (itching, swelling around the eyes, runny nose, watery eyes, hives, etc.).

Benadryl can help a Chihuahua by blocking the histamine. It does not cure the allergy, it temporary decreases the symptoms. As the medicine wears off, if the body is still reacting to the allergen, symptoms will reappear. 

Reasons to give Benadryl to a Chihuahua

For long term allergies with chronic issues such as major itching, a thinning coat, and other troubling concerns, you'll want to look to more permanent treatment including reducing or eliminating triggers and using topical treatments, both of which can be done at home in many cases. However, you can give Benadryl to a Chihuahua puppy or dog for acute allergic reactions in which the dog needs fast treatment.

Some examples of this are:
  • Reaction to an insect sting 
  • Minor side effects from a vaccination (beware that moderate to severe adverse reactions to any vaccine must be professionally treated with epinephrine and oxygen treatments to prevent sometimes fatal conditions of anaphylaxis) 
  • Stuffy nose 
  • Runny nose 
  • Watery eyes 
  • Slight coughing  
  • Minor hives 
  • Slight to moderate acute itching  
  • It also works to combat motion sickness for some dogs

How Fast Benadryl Can Work

Once you give your Chihuahua the proper dose of liquid Benadryl, it will begin to work within 10 to 30 minutes.

If you do not see any improvement after a half hour, this means that the medicine is not going to resolve the issue that your puppy or dog is having. It is important to not give any more Benadryl, as an overdose is dangerous.  

Benadryl Dosing Chart for Chihuahua Dogs 

How much Benadryl you should give to a Chihuahua puppy or dog will depend on his or her weight. Therefore, a 5 pound puppy will receive the same amount as a 5 pound senior dog. Correct dosing is not dependent on age.
The key element to keep in mind is that if you give too little of the medicine, it will not have the desired effect. It you give too much, there will be an issue of overdosing.

Dosing is done by milligrams. The easiest method is to offer the tablet form of Benadryl. And it is easy to remember, because the dosing is 1 mg for each 1 pound of body weight: 

Here is an easy chart to follow:

Chihuahua Weight     Dosing Amount

.5 lbs. (.22 kg)             .5 mg 
1 lb. (.45 kg)                1 mg
2 lbs. (.90 kg)               2 mg
3 lbs. (1.36 kg)             3 mg
4 lbs. (1.81 kg)             4 mg
5 lbs. (2.26 kg)             5 mg 
6 lbs. (2.72 kg)             6 mg
7 lbs. (3.17 kg)             7 mg
8 lbs. (3.62 kg)             8 mg
9 lbs. (4.08 kg)             9 mg
10 lbs. (4.5 kg)            10 mg 

If you choose to use liquid Benadryl, the dosing is 0.4 ml for each 1 pound of body weight. Using a medicine syringe that shows dosing in milliliters is recommended to ensure that you offer the correct amount. 

How Often to Give a Chihuahua Benadryl

If the first dose has worked to bring an allergic reaction to a stop and is controlling symptoms, you can give a dose every 8 hours. If is appears that it is not working, do not give a more to your Chihuahua before the 8 hours; ongoing problems that are not responding to Benadryl is your sign that your puppy or dog needs to be taken to the veterinarian.

For acute issues, this over-the-counter medication is usually given for 3 days. If your Chihuahua is having trouble beyond this amount of time this points to a more chronic condition that should be evaluated by a professional.

Side Effects

You may wonder what will happen if you give Benadryl to your Chihuahua. This is considered a safe medication and is often used by veterinarians. If you give the correct amount as shown above, the most common side effect is sleepiness.
In some cases, it can actually have an opposite effect, causing some initial energy. However, with most puppies and dogs once the medicine kicks in and the stress of the allergic reaction subsides, the dog can become really tuckered out.

Benadryl has moderate to severe sedating qualities and this is one reason why you want to take care to not give your puppy or dog too much.

The most common and normally mild side effects that a Chihuahua may experience are:
  • Drowsiness
  • Drooling 
  • Rapid breathing 
  • Rapid heartbeat 
  • Depression 
  • Dry mouth 
  • Excitability  
In most cases, these effects wear off within one hour. If your Chihuahua has a bad reaction to Benadryl, be sure to take him to the closest animal hospital or veterinarian right away.

Severe Side Effects and Overdosing

Even if you have given Benadryl to your Chihuahua in the past, you will want to keep an eye on your puppy or dog to make sure that he is not experiencing any severe adverse side effects.

Additionally, if too much was accidentally given to a Chihuahua, his body may experience an overdose. Red flags to look out for include:
  • Sudden agitation 
  • Extreme drowsiness 
  • Sudden aggression 
  • Abnormal heart rate 
  • Muscle tremors 
  • Fever 
  • Abnormal behavior
  • Difficulty breathing

Giving Benadryl to a Chihuahua with Motion Sickness

If your Chihuahua becomes ill when being driven in the car, you may be wondering if Benadryl will help a Chihuahua with motion sickness. Motion sickness happens when the body has trouble making the connection with the eyes and inner ears when there is movement such as being in a moving car.

Once suffering from this, a Chihuahua may hate being in the carA dog may have a queasy stomach that leads to vomiting and drooling and/or heavy panting due to nausea and dizziness. 

Antihistamines work to combat this by affecting the part of the brain that controls both nausea and vomiting.
Since this medication can make a puppy or dog very sleepy and does have some possible side effects, it is first recommended to implement techniques such as keeping the dog in a raised canine car seat where he has better access to the air from an open window and by feeding some light biscuits about 20 minutes before leaving but not giving a full meal until after the ride is complete.

If this does not work, you can give a Chihuahua Benadryl for car sickness if it is only done on occasion and by following the recommended dosing. After checking with the vet and receiving approval, you would give a dose roughly 20 minutes before you plan to bring your Chihuahua into the car. The added benefit to the side effect of drowsiness is that a puppy or dog may sleep right through the ride and awake once it is over.

Even with this treatment, you will still want to be sure to have your Chi safe in a canine car seat and provide adequate fresh air for the duration of the trip.

Danger Alert - Make Sure You Give a Chihuahua the Right Benadryl

Be careful when you choose the medicine. Some brands of diphenhydramine are packaged to look like Benadryl (same colors, etc.) but contain ingredients that can be very harmful and often fatal to dogs. You will want to carefully check the label and NOT obtain any medicine that contains acetaminophen, pseudoephedrine, or alcohol. The ingestion of these substances can be fatal.

Only diphenhydramine should be given by following the proper guidelines listed above or by following the advice of your Chihuahua's veterinarian.

This site provides general information and should not be considered medical advice for your puppy or dog. You should always check with your Chihuahua's veterinarian before deciding on a treatment option for your pet.
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