Pollens, mites, animal dander, food… In contact with certain allergens, it happens that notre immune system gets carried away : it begins to produce an abnormally high quantity of lgE antibodies before releasing histamine, which is responsible for expelling allergens from the body and causes a host of symptoms : sneezing, watery eyes, coughing, itching, etc.
Fortunately for those affected, there are specific drugs, called antihistamines, capable of preventing — or at least limiting — the effects of histamine. How do they work? Can you get them over-the-counter? What are their side effects? Answers from Dr Jean-Marie Nguyen, allergist doctor at Bicêtre Hospital and member of the association Asthma and Allergies.
Definition: what is an H1 antihistamine?
As stated above, antihistamine medications help to counter the action of histamine. They have therefore been used for nearly fifty years to fight once morest allergic symptoms. Concretely, the H1 antihistamines block histamine receptors, which prevents said histamine from attaching to these receptors and triggering allergic symptoms.
They therefore do not act on the cause of the allergy, but they can have a preventive effect (when taken before exposure to an allergen) or a curative effect (they can reduce the symptoms once these ci triggered).
Good to know: in case of severe allergy, they are revealed sometimes ineffective and must be replaced by other more suitable drugs, emphasizes Dr. Nguyen.
What is the difference with H2 antihistamines?
“H2 antihistamines are not used to treat allergies. They are generally recommended in the management of gastric problemsto reduce the secretion of gastric acid in the context of GERD, for example”, answers the allergist.
Tablets, eye drops, syrup, nasal solutions… H1 antihistamines are available in several forms
H1 antihistamines may be prescribed for adults as well as children. They are usually offered as medications to take orally (tablets, capsules, syrups), but they can also be used locally in the form:
- of eye drops (azelastine, levocabastine, emedastine and olapatadine);
- of solutions nasales (azelastine) ;
- of creams or of gels (promethazine, diphenhydramine).
Indications: which H1 antihistamine type for which allergy?
H1 antihistamines may be indicated in the management of spontaneous seizures or persistent pathology such as allergic rhinitis (hay fever), a allergic conjunctivitisof a urticaria or a eczema. In any case, they will allow the deleterious symptoms to be controlled and the patients will regain their comfort more quickly.
“After a certain time, it is possible that a molecule becomes less effective on certain patients. We are talking regardingexhaust effect, says Dr. Nguyen. In this case, it is better to test a new molecule which may prove to be more effective”.
Moreover, in case of’allergic asthmaanaphylactic shock or edemathese drugs are unfortunately not sufficient to overcome the symptoms.
First or second generation: which are the most effective antihistamines (list)?
H1 antihistamines can be classified into two groups: first-generation antihistamines and second-generation antihistamines.
- First-generation antihistamines, also called anticholinergics, are older, not very specific for histamine receptors and often more sedating. Among the best known: alimemazine (Théralène®), brompheniramine (Dimégan®), cyproheptadine (Periactin®), dexchlorpheniramine (Polaramine®), doxylamine (Donormyl®), hydroxyzine (Atarax®), ketotifen (Zaditen®), mequitazine (Primalan®), oxomemazine (Toplexil®) and promethazine (Phenergan®).
- Second generation antihistamines, they are more specific for histamine receptors and have fewer adverse effects. Among the best known: bilastine (Bilaska®, Inorial®), cetirizine (Zyrtec, Virlix®), desloratadine (Clarinex®, Aerius®), ebastine (Kestin®), fexofenadine (Telfast®), levocetirizine (Xyzall®), loratadine (Clarytine®), mizolastine (Mizollen®) and rupatadine (Wystamm®).
Sensitivity to molecules varies from person to person, but the focus is generally on second-generation antihistamines, says Dr. Nguyen. First-generation antihistamines are on the way out.
What antihistamines are available without a prescription?
A reaction to an insect bite? A weekend in a dusty renovated barn? Occasional exposure to a pet you are allergic to? For this, there are many antihistamines available over the counterin pharmacy : Benadryl®, Cétirisine Mylan Pharma®, Doli allergie®, Humex® allergie, Reactine®, Zyrtecset®.
Just as effective as prescription antihistamines, however they are not not reimbursed and may be slightly more expensive. If you opt for this type of medication, do not hesitate to ask your pharmacist for advice, who will be able to guide you as best as possible depending on the situation. Strictly respect the dosage and duration of treatment indicatedon the note and make an appointment with a doctor if symptoms persist or worsen.
What antihistamines are available by prescription (list)?
Among the most prescribed antihistamines are: Aerius®, Bilaska®, Clarityne®, Kestin®, Virlix®, Xysall® or Zyrtec®.
Can you take cortisone and an H1 antihistamine?
As a reminder, cortisone is a corticosteroid drug generally prescribed to treat inflammation and serious allergies. It is generally possible to combine it with an H1 antihistamine. It may even be recommended in some cases, to treat severe allergies or inflammation.
“And in the event of a serious allergy, if that is not enough, we can go through desensitization, in other words, targeted immunotherapy once morest a specific allergen, points out Dr. Nguyen. This management is sometimes carried out over several years and consists of exposing patients to progressive doses of allergens to accustom their body and ensure that it stops triggering inflammatory reactions.
Can we consume alcohol, anxiolytics or antidepressants while on antihistamine treatment?
It is generally not recommended to consume alcohol (even in small quantities)antidepressants or anxiolytics along with antihistamine therapy. Because ? This can increase side effects such as drowsiness, fatigue, and dizziness. If however you were to “mix” anxiolytics, antidepressants, alcohol and antihistamines, it is strongly advised once morest driving.
Drowsiness, nausea, dry mouth… What are the side effects of these anti-allergy medications?
The side effects of antihistamine drugs are unfortunately well known, in particular the somnolence. In theory, second-generation antihistamines cause fewer side effects, but some people are still very sensitive to them. “Everyone reacts differently depending on the molecules, doses used, body size, etc. It is also difficult to distinguish fatigue related to allergy symptoms from fatigue related to taking antihistamines,” notes Dr Nguyen.
Other side effects may also occur:
- of the dizziness ;
- of the nausea and vomiting ;
- a dry mouth feeling and of intense thirst ;
- a dry eye and an mild visual impairment ;
- a constipation (antihistamines can indeed reduce intestinal motility);
- of the difficulty urinating (antihistamines can reduce the ability of the bladder to empty completely);
- etc.
These side effects are normally mild and temporary! If they persist or worsen, consult a healthcare professional.
In video: “Can we cure a respiratory allergy?”
To find out more regarding respiratory allergies, visit the association’s website Asthma & Allergies. Its main objectives? Inform and support patients with asthma or allergies, parents, as well as doctors and healthcare professionals. You can also contact their green number: 0800 19 20 21 (free call).