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Doctor insights on: Antihistamine Tolerance

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I have noticed that my body is immune to loratadine based antihistamines (doesn't make me tired) but any others do. Does this means tolerance?

I have noticed that my body is immune to loratadine based antihistamines (doesn't make me tired) but any others do. Does this means tolerance?

Non-sedating: Loratadine is considered a non-sedating antihistamine. It is supposed to treat allergic symptoms without making you drowsy. Other older antihistamines like benadryl (diphenhydramine) are very sedating.

Tolerance (Definition)

When one takes a drug, such as heroin or alcohol, repeatedly, 'tolerance' develops because more of the drug is needed to give the same effect on the body/brain; e.g. Liver enzymes r stimulated to metabolize the drug faster and faster. There may be a strong genetic predisposition to addiction, some studies suggesting that 1 of 10 people will become dependent on alcohol or some ...Read more


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What is the best OTC antihistamine?

OTC antihistamines: The second generation zyrtec, allergra or Claritin (loratadine) are comparative. None are perfect. Zyrtec is slightly more likely to make you tired ot sleepy. Often one works a little better than another and I adise you to test all three.

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Is antihistamine harmful to the body?

Is antihistamine harmful to the body?

No: Antihistamines are a class of medication used since the 1940s. They are used to treat allergic conditions and are very safe. The newer generation antihistamines have even less side effects compared to first generation or old antihistamines.

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When should you take an antihistamine?

When should you take an antihistamine?

Multiple reasons: Depending on the type of antihistamine used they can be used to treat things such as allergy symptoms, nausea, dizziness, motion sickness, anxiety, itching, and difficulty sleeping.

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What are the common uses of antihistamine?

What are the common uses of antihistamine?

Antihistamine 4 itch: Antihistamines (ah) block histamine receptors and stop histamine from causing itching and swelling. They are mainly used to treat allergies and hives. Some are sedating; those are used as sleep aids. Many otc sleep meds contain Diphenhydramine (benadryl).

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What is the best time to take an antihistamine?

Any time: You can take antihistamines any time of the day. Take them same time of day everyday.

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Why young people more sensitive to antihistamine?

Why young people more sensitive to antihistamine?

Not true: Everyone reacts to medications differently although the differences may be minor in most cases. There is no study showing that young people are more sensitive to antihistamine, especially the newer ones.

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Can I die by taking too many antihistamine tablets?

Can I die by taking too many antihistamine tablets?

Taking lethal over: Dose would do that. Lethal overdoses of antihistamines are rare. Are you considering taking an overdose of antihistamines? If so, please get help right away. You can use national suicide hotlines 24/7 at 1-800-suicide (1-800-784-2433) or 1-800-273 – talk (1-800-273-8255). If you have accidentally taken too many antihistamines please contact 1-800-222-1222 (poison control hotline). Take care.

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What is the safest antihistamine for long term use?

What is the safest antihistamine for long term use?

New generation ones: Antihistamines in general are very safe. New generation products (Zyrtec, Claritin, (loratadine) Allegra, Xyzal) are just as effective with less side effects than older antihistamines (Benadryl, chlorpheniramine, hydroxyzine). However, it would be important to address WHY a person needs to take antihistamines long term? Consult with an allergist to assist in identifying the cause of symptoms.

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Help please? What is a good yr round OTC antihistamine?

Antihistamine: All are good, zyrtec, allegra and claritin, (loratadine) but you should see an allergist if you need medicine all year round

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Can I vaccinate my son while he is taking antihistamine?

Can I vaccinate my son while he is taking antihistamine?

Yes: The drug will not affect the success of the vaccination or cause any negative reaction.

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Can you tell me what is the best medicine for antihistamine?

Can you tell me what is the best medicine for antihistamine?

New generation ones: The new generation antihistamines include Claritin, Zyrtec, Allegra and Xyzal (levocetirizine). These are as effective as older antihistamines (Benadryl, hydroxyzine, chlorpheniramine). Each person may respond differently to the different products and therefore trying them one at a time can be helpful. Since they are over-the-counter and generic (except for Xyzal (levocetirizine)), they are affordable and available.

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Is it possible to die from an overdose of antihistamine pills?

Is it possible to die from an overdose of antihistamine pills?

Which one: First generation antihistamines are sedating, second generation ones are not, overdosing on the latter hardly kills, but may cause sedation. Overdosing on first generation antihistamines may be more of a problem, but again they are safe in high doses.

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How many milligrams of antihistamine can a person take at one time?

Unclear: Different antihistamines have different potencies. 10 mg of Zyrtec is equivalent to 180mg of Allegra (fexofenadine). Mg doseage as in all medicines are drug specific. In regard to toxic levels, each has it's own known limit. However too much antihistamine can lead to deadly arrythmias/ Please use the recommended dose.

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Is vistral and antihistamine the same or are they common medication?

Is vistral and antihistamine the same or are they common medication?

Antihistamine: Any medication that blocks chemical histamine, which causes allergy, is antihistamine. Vistaril (hydroxyzine) is one of these antihistamines. It is also used for sleep and sedation.

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What is the average time needed for an antihistamine to begin to work?

45-90 minutes: Antihistamines taken by mouth begin to work in about an hour but may take longer if you've just eaten. Antihistamine nasal sprays (astepro, patanase) begin to work in 30 minutes. An antihistamine injection, usually diphenhydramine, sometimes given for a severe allergic reaction or anaphylaxis begins to work in a few minutes.

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What is the highest dosage of antihistamine that one person can take at one time?

Antihistamines: Safety of high dose medications is often unknown. Our experience comes from case reports of persons who intentionally or accidentally consumed unusually excessive quantities. When Claritin (loratadine) was first investigated, safety studies were done at 40 mg (4 times the current recommended dose). We take 10 mg because effectiveness is not significantly different between 10 mg and 40mg.

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Dr. Paul Carter
634 Doctors shared insights

Antihistamine (Definition)

Sedating and non-sedating antihistamines prevent and treat allergic reactions, and are ...Read more