Pam asked
My allergist is on the fence about whether I have Oral Allergy Syndrome and/or Mast Cell Activation Syndrome, which could be the cause of some of my food reactions. I am trying to start preventative allergy meds, to follow the MCAS "protocol" of H1 and H2 antihistamines. I have been taking Claritin daily for a couple of weeks. He wants me to add a second dose of an H1 antihistamine first before adding the H2, like a Pepcid or Zantac. But the bottle of Claritin is pretty clear it's 1 per day. Can I take a Zyrtec or Allegra with it, as the allergist suggests, or is this risky? If I need Benadryl due to an unforeseen reaction to a food, can I take a dose of that on top of 2 H1 doses a day? Is there any problem with taking 2 plus Tylenol for my kidneys and liver? I just don't have a lot of options, but I really need to do more to treat the allergies proactively. Thank you.
Answer
Antihistamine medications are generally seen as a first-line therapy for the treatment of symptoms associated with Mast Cell Activation Syndrome. Specifically, second and third generation antihistamines (also known as "H1-blockers) are preferred due to their long duration of action, effectiveness and lack of side effects. Second and third generation antihistamines include:
- Claritin (loratadine)
- Allegra (fexofenadine)
- Zyrtec (cetirizine)
- Xyzal (levocetirizine)
All of the above antihistamines are indicated for once daily dosing (except if using a dose for children). However, in certain situations, your doctor may recommend them to be dosed "off-label" at higher strengths. There have been a few studies that found taking twice the normally recommended dose of Zyrtec (cetirizine) or Claritin (loratadine) can be effective in further reducing allergy symptoms while still being relatively safe and free of major side effects.
Double Dose Of Antihistamine Studies
One study, published in the Journal of Dermatological Treatment, found that a "double dose" of Zyrtec (cetirizine) was more efficacious for refractory urticaria (i.e. hives) when compared to the regular dose of cetirizine (10mg and 20mg respectively). Another study, published in the British Journal of Dermatology found similar results with no significant increase in adverse effects.
High doses of Claritin (loratadine) have been explored as well and have been shown to be effective in certain situations, with few adverse effects. In fact, one study published in the Journal of International Medical Research found that 40mg of loratadine (versus the recommended 10mg dose) was effective and had no adverse effects.
Based on the available data, you may see some benefit from taking higher doses of antihistamines than indicated, especially as you are potentially treating a disease in which excess histamine is released from mast cells. There haven't been studies that have detailed use of two different antihistamines together (e.g. Allegra with Claritin), but the concept would be the same and may be worth a try for your condition per the recommendation from your doctor.
Nevertheless, you want to watch out for potential antihistamine side effects which include:
- Sedation
- Dry mouth
- Dry eyes
- Constipation
- Heart palpitations (rare)
Taking more than the recommended doses may increase the risk of the above side effects, but most studies of the second and third generation antihistamines listed above show they still tend to be well tolerated, even at higher doses.
Using H1 And H2 Blocker
Treatment guidelines for Mast Cell Activation Syndrome recommend using an H2 blocker, such as Tagamet or Pepcid, in conjunction with a traditional antihistamine like Claritin. The combination of both is fairly common. Several studies, such as this one published in the Annals of Emergency Medicine, find that the combination of H2 blockers and H1 blockers can provide more relief of allergy symptoms than either alone, especially symptoms of itching. We recently wrote an article on this subject which can be found here: Does Tagamet (Cimetidine) Work For Allergies?
H2 Blockers that are commonly used in conjunction with H1 blockers include:
- Pepcid (famotidine)
- Tagamet (cimetidine)
- Zantac (ranitidine)
Can You Take Benadryl With Your Antihistamine?
In general, it isn't recommended to take two antihistamines together but one common exception is for Benadryl. Benadryl has been shown to be more effective than other antihistamines in stemming symptoms of an allergic reaction such as itching and swelling. Even if you are taking a daily antihistamine like Claritin, your doctor may recommend Benadryl to be taken as needed. This in most cases is safe, but may increase antihistamine side effects such as drowsiness and dry mouth.
Other Treatment Options for Mast Cell Activation Syndrome
In addition to antihistamines, other treatment options include:
- Cromolyn: A mast cell stabilizer which helps to prevent histamine and other inflammatory mediators from being released into circulation. Cromolyn is available as a nasal spray and nebulizer solution.
- Vitamin C: Decreases histamine formation.
Very often, a combination of drugs is recommended (e.g. H1 blocker, H2 blocker, Cromolyn and Vitamin C) at the same time for best relief.
Aside from the first line therapy options, a variety of other drugs are recommended based on symptoms and severity. This article published in Naunyn-Schmiedeberg's Archives of Pharmacology gives a comprehensive run-down.
Additional Information
Tylenol, in addition with the other medications listed above, is considered safe to take as long as you do not exceed the recommended dose of 4,000mg per day.
