Doctor insights on:
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?
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
Can a certain antihistamine stop working when taking to help with insomnia or skin rash and you need to switch to another? Tolerance?
Antihistamines: Possible, with continued regular use.Get a more detailed answer ›
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. ...Read more
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. ...Read more
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. ...Read more
Yes: Butterbur has antihistamine-like effects. It can be found at health food stores. ...Read more
Yes: The drug will not affect the success of the vaccination or cause any negative reaction. ...Read more
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. ...Read more
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. ...Read more
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. ...Read more
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. ...Read more
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. ...Read more
I know it is not recommended to take more than one antihistamine pill per 24 hours, but some only last ~8 hours. Which ones lasts for 24 hrs?
Xyzal (levocetirizine) and Clarinex: From experience some of the newer antihistamines such as Xyzal (levocetirizine) and Clarinex seem to be effective for longer time periods. Most antihistamines however peak in effectiveness in the first few hours and start to wear off after 12-15 hours. ...Read more
The newer ones: Antihistamines can cause sedation by entering the brain's tissue and binding to h1 receptors. (called "crossing the blood brain barrier".) that effect is desirable if you are taking an antihistamine for sleep (e.g. Benadryl). The newer antihistamines don't cross the blood brain barrier as much. These include (least to most sedate) fexofenadine (allegra), Cetirizine (zyrtec), loratidine (claritin). ...Read more