​In histamine intolerance, symptoms may be caused by active substances that inhibit the breakdown of histamine

​These medications inhibit the DAO enzyme, although recent scientific data on this is contradictory. This group includes commonly used drugs such as Diclofenac (Voltaren), Coldrex, ACC, Algopyrin, etc. Therefore, for migraine headaches, it is advisable to use Paracetamol (e.g. Ben-U-Ron, Panadol) instead!

​Acetylcysteine • Alcuronium • Alprenolol • Ambroxol • Amiloride • Aminophylline • Amitriptyline • Cefotiam • Cefuroxime • Chloroquine • Cimetidine • Clavulanic acid • Cyclophosphamide • Dihydralazine • Dobutamine • Isoniazid • Metamizole (e.g. Analgin) • Metoclopramide • Metronidazole • Morphine • Pancuronium • Pentamidine • Pethidine • Prilocaine • Propafenone • Thiopental • Thiamine • Verapamil • Isoniazid • Furosemide • Diclofenac • Aspirin (acetylsalicylic acid) • Radiographic contrast agents

​Dietary supplements can also block enzymes! A good example is caffeine (found in coffee and energy drinks) and the theophylline, theobromine, etc., found in chocolate.

 HNMT-inhibiting medications: Amodiaquine • Metoprine • Tacrine • Diphenhydramine (e.g. Dramamine)

​Medication treatment

​Briefly:
Treatment targets histamine receptors, of which there are four types: H1, H2, H3, and H4. Medications are only available for the first two.
Additionally, DAO enzyme supplements can be taken, which break down histamine in the intestinal lumen. This means the supplement is only effective while food is present in the intestines.

Example of such a treatment: Cetirizine 1 tablet + Famotidine (Quamatel) 40 mg 1 tablet + NATURDAO 1 tablet (before, during, or immediately after the meal — the sooner, the better).

In more detail:
H1 receptor blockers, also known as antihistamines, are available over the counter in pharmacies. Desloratadine and cetirizine are good options. Usually, one tablet per day is required. Since drowsiness is a possible side effect, they are best taken in the evening. Under medical advice and supervision, a double dose of antihistamines may also be tried.
H2 receptor blockers are used to reduce stomach acid. Among these, Quamatel Mini is available without a prescription. The typical daily dose is 2 × 40 mg, as advised by a doctor.
By taking both medications together, the effects of histamine on H1 and H2 receptors can be reduced. However, this does not affect the H3 receptors (located in the brain) or H4 receptors, so it is not a complete solution.
 
Despite research, I have not found pharmacological profiles for DAO enzyme supplements. As they are classified as dietary supplements, they have not been studied in detail. This enzyme is not absorbed into the bloodstream — it only breaks down histamine in the intestines. Therefore, it only helps while histamine is still present in the gut. Moreover, it cannot counteract the effects of "histamine-releasing" or "DAO-blocking" foods.
  
Unfortunately, this means that the above medications offer only a partial solution, and DAO enzyme supplements are only effective if taken during or immediately after meals. The effects of antihistamines (H1 blockers) and H2 blockers take a few hours to develop, by which time symptoms may already be subsiding. They may help a little in the case of dietary mistakes if taken before, during, or right after a meal.
In my subjective opinion, they are not particularly helpful for persistent symptoms.
I do not recommend any other products or supplements — only a varied, healthy diet! 

​What is the professional opinion on IgG food intolerance?

​Without citing detailed professional references, it is well known that no medical journal, allergy society, or professional association currently recognizes its usefulness. We do not fully understand why IgG-type food antibodies are present in our bodies. It is most likely simply a marker of what we have been exposed to.
In my experience, those who have undergone this type of test generally did not achieve dramatic success with the diet. Many started the IgG-based diet but eventually discontinued it because it did not bring the expected results. I have never encountered anyone who became COMPLETELY symptom-free from the diet — only those who experienced moderate improvement.
That said, the test might still prove to be useful, but we need to find its proper place and appropriate application. It certainly does not indicate that an entire food group should be eliminated!