Gut flora and allergies: Do probiotics really work?

There is currently no absolute "yes/no" answer to this question. Specific strains do have clear intervention effects on specific types of allergies. However, the vast majority of Internet celebrity probiotics on the market that promote "allergy cures" are basically IQ-taxed.

Two years ago, I met a 3-year-old baby with milk protein allergy when I was attending a child nutrition clinic. My mother spent more than 2,000 yuan at a maternal and child store to buy imported probiotics that are said to "regulate allergic constitution." She took them for two months, but the rash on the corners of her mouth and the diarrhea after drinking milk were not relieved at all. Later, she did an allergen screening and intestinal tract examination. For flora testing, the doctor prescribed medical probiotics with Lactobacillus rhamnosus LGG and Lactobacillus reuteri DSM17938, which were combined with deeply hydrolyzed milk powder for more than three months. During the reexamination, the specific IgE index dropped by nearly half. Later, I slowly switched to moderately hydrolyzed milk and no allergic reactions occurred.

Why are the same probiotics so different? In fact, the academic community has basically reached a consensus on the relationship between intestinal flora and allergies. The first 12 months after birth is a critical window for intestinal flora colonization, which coincides with the development and maturation cycle of the immune system. If at this time, due to reasons such as cesarean section, excessive disinfection, and premature use of antibiotics, the diversity of the intestinal flora is insufficient and some key strains are missing, immune cells will easily "disrecognize the good guys" and treat originally harmless substances such as pollen and food proteins as invaders to repeatedly attack. This is how allergic reactions occur.

But when it comes to the specific role of probiotics, the academic community is still very noisy. On the one hand, more and more clinical studies have supported the role of specific strains. For example, a long-term cohort study published in the "Journal of Allergy and Clinical Immunology" in 2023 showed that continuous supplementation of a combination of Lactobacillus rhamnosus LGG + Bifidobacterium lactis Bb-12 from late pregnancy to before the baby is 6 months old can reduce the risk of food allergy and atopic dermatitis in children under 3 years old by 32%. ； But on the other hand, many studies have raised objections. If the intestinal flora is not obviously disordered, blindly supplementing probiotics of unknown strains will crowd out the living space of the original bacteria and disrupt the balance of the original flora. I met a girl suffering from seasonal hay fever last year. I read about Amway on the Internet and took probiotics from a certain Internet celebrity for three months. Initially, I only suffered from sneezing and runny nose due to the change of seasons. Later, I even developed symptoms of red and swollen eyes and itchy skin. I checked the flora and found that the proportion of Bifidobacterium that was originally dominant in her was reduced by nearly 20%, which was not worth the gain.

If you carefully read the promotion of probiotics, you will find that many merchants will only label the bacterial species names such as "Bifidobacterium" and "Lactobacterium" and do not dare to label the specific strain number - to put it bluntly, this is the biggest pitfall. Different strains of the same species can have very different effects. Take Bifidobacterium lactis as an example. HN019 mainly regulates intestinal peristalsis, while Bl-04 is the one that relieves some upper respiratory tract allergies. If you buy the wrong strain, it will be useless no matter how much you eat. What's more, the coating technology of many affordable probiotics is not up to standard, and the live bacteria cannot survive the corrosion of gastric acid and bile. They are already dead by the time they reach the intestines, which is no different from drinking some bacterial powder and sugar water.

Of course, don’t think that probiotics are all a lie. Nowadays, specific strains of probiotics have been included in the recommendations of clinical guidelines for the prevention and auxiliary relief of mild to moderate atopic dermatitis in infants and young children and some food allergies. However, for problems such as allergic asthma and severe allergic rhinitis, there is currently not enough large-scale clinical evidence to prove the effect of probiotics. Don’t foolishly stop taking anti-allergic drugs and only take probiotics, which will delay the condition.

If you really want to try using probiotics to treat allergies, don’t just blindly buy them from the e-commerce details page. Go to an allergist department or clinical nutrition department for evaluation first. If necessary, combine the intestinal flora test results and choose products with clear strain numbers and clinical evidence support. Eat them for a 3-6 month period. At the same time, you can make basic adjustments such as avoiding allergens and using less broad-spectrum disinfectant products. Only then can you really see the effect.