The Benadryl , also known as diphenhydramine, is an antihistamine drug used to combat, reduce or eliminate the effects of allergies on the body, blocking temporarily production of histamine (chemical that is released in the body when it occurs an allergic reaction).

4 types of histamine H1, H2, H3 and H4 receptors are known, in this sense that antagonist of the H1 receptor is considered an antihistamine agent. These antagonists play a fundamental role in the inhibition of hormones and also block the ability to act as a neurotransmitter.

If you are interested in knowing more about the properties, uses, doses, presentations, effects and contraindications of this drug, do not miss this interesting reading.

Indications of benadryl

It is used to treat:

  • Runny nose.
  • Tearing
  • Itchy throat and nose.
  • Sneezing
  • Cold symptoms.
  • Feeling tired.
  • Allergic conjunctivitis.
  • Urticaria.

Produced by allergies to pollen, animals and any other allergenic agent that the immune system considers foreign.

In addition, it is used to treat the effects of dizziness produced by movement, it is also used to cause or induce sleep and combat some symptoms produced by Parkinson’s disease.

What you should know and discuss with your doctor before taking this medicine

If you have certain pathological conditions, you should inform your doctor in advance, among them are:

  • Urinary problems or bladder obstruction.
  • Liver diseases or disorders.
  • Digestive tract blockage.
  • Glaucoma.
  • Renal disease.
  • Breathing disorders such as asthma or any other lung disease.
  • Thyroid gland disorder.
  • Emphysema, cough with mucus, chronic bronchitis, or cough caused by smoking.
  • High blood pressure or cardiovascular disease.
  • If you take medicines that contain potassium.

According to the FDA pharmacological bulletin, this drug is in pregnancy category B so it is not considered to harm the fetus, however, it is recommended that you consult this information with your treating physician.

It is proven that the drug is excreted through breast milk so it should never be used if you are breastfeeding.

Older adults tend to manifest more often the side effects produced by its consumption.

How the medicine or treatment is applied

Generally its indication is made by a specialist or treating physician, it should not be consumed for long periods since generally the symptoms caused by allergies or colds disappear in a couple of days.

Never consume more than the dose established by the specialist and always use the correct utensils to take measurements.

In people with sleep disorders or difficulty sleeping, it is recommended to take your dose 30 minutes before going to sleep.

To counteract the effects of motion sickness (travel on curvy roads, airplanes, boats, or amusement park) take a dose 30 minutes before being in the above situations. If you are in a situation for a time longer than 24 hours and less than 72 hours, you can consume a dose 30 minutes before each meal during this time.

Pharmaceutical formula

Each 100 ml of SYRUP contains:

  • Diphenhydramine hydrochloride 0.25 g.
  • Vehículo, c.b.p. 60 ml.

Each vial contains:

  • Clorhidrato de difenhidramina 100 mg.

Recommended dosage


  • Adults: 5 ml every 6 to 8 hours.
  • Children 3 to 5 years: 2.5 ml every 8 hours.
  • Children 6 to 12 years: 2.5 ml every 6 hours.
  • Maximum dose given per day for children 3 to 6 years 25 mg.
  • Maximum dose given per day for children 6 to 12 years 50 mg.

Injectable solution:

  • Adults and children over 12 years: 10 to 50 mg every 8 hours.
  • Maximum dose, 400 mg / day.
  • Children 3 to 12 years: 5 mg / kg / day.
  • Maximum dose, 300 mg / day.

While taking the medicine avoid the following

  • Avoid driving vehicles or heavy machinery, be very careful when doing so, among some recognized side effects is blurred vision and eye fatigue, its lethargic effect and low motor reaction are also considered.
  • Do not consume alcohol as it stimulates the manifestation of side effects.
  • Do not consume other self-medicated or over-the-counter medicines, always ask your specialist before consuming any other pharmacological product. In case you do not have a nearby doctor, check the formula of any other medicine to make sure that they are not composed of other antihistamines (if so, discontinue use).

In case you forget a dose, what should you do?

If you miss a dose you can consume it as soon as you remember, if the time for the second dose is approaching, wait for it and never take a double dose to replace the forgotten one, remember that benadryl is used when your body requires it so you can being on an off-dose schedule.


The use of this medicine may affect the results or tests carried out to determine certain allergies that attack the body.

The use should not be recommended to other people to treat similar illnesses or with distinctive symptoms, always consult your doctor for instructions.

If after a couple of days applying the treatment you do not observe any change or any improvement, discontinue its use and consult your doctor.

Side effects

Some significant effects of an anaphylactic reaction are:

  • Swelling of the face
  • Difficulty breathing.
  • Swelling obstruction in the throat.
  • Skin rash.
  • Swelling of the lips and tongue
  • Other effects that may occur:
  • Dry mouth, throat and nose.
  • Dry eyes and eye strain.
  • Pounding heartbeat
  • Abdominal pain.
  • Difficulty getting to sleep.
  • Discomfort to urinate, in this sense urinating little or almost nothing.
  • Dizziness and lack of motor coordination.
  • Feeling faint and lack of energy.
  • Sensitivity of the skin to sunlight.
  • Stiffness in some parts of the body such as the neck or jaw.

It is recommended that, if you suffer from any of these effects or any other that is not specified in the previous list, you stop the treatment and consult your doctor immediately.


Before consuming this medicine, inform your doctor of any pathology suffered that may affect or restrict its application:

  • Bronchial asthma.
  • Lung diseases.
  • Prostatic hypertrophy.
  • Gastrointestinal diseases.
  • Liver diseases or disorders.
  • Pregnant women (consult a specialist doctor beforehand).
  • Lactating women.

How to store and dispose of benadryl

Always keep the product in its original packaging and preferably closed, out of the reach of children and at a temperature below 30 °, please do not expose to sunlight or in humid places. Never share your medicine with other people and use it only for the prescribed purposes and in the recommended dosage.

To dispose of any type of medicine to avoid accidental ingestion by animals or children, ask your nearest pharmacist about the medicine collection and disposal plan.

In case of accidental ingestion

  • In children it can be fatal so you should go immediately to the nearest health center in your community.
  • You can develop toxic encephalopathy or psychosis.
  • Adults often show lethargy and motor difficulties, they also have extreme drowsiness or coma after receiving an overdose, however, overdose in young children causes excitement, visual hallucinations, seizures, hyperactivity, irritability, insomnia. and euphoria.
  • People with overdose usually have anticholinergic effects, among these effects are dry throat, mouth and nose, as well as fever and headache, pupillary dilation, flushed face, difficulty urinating, decreased motility gastrointestinal causing nausea, vomiting, diarrhea, abdominal pain and hypotension.

General support measures such as evacuation of gastric contents, use of anticonvulsants and hemodialysis are used to treat a person with overdose.

Samantha Robson
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Dr. Samantha Robson ( CRN: 0510146-5) is a nutritionist and website content reviewer related to her area of ​​expertise. With a postgraduate degree in Nutrition from The University of Arizona, she is a specialist in Sports Nutrition from Oxford University and is also a member of the International Society of Sports Nutrition.

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