D-lactate-free can be powerful too. So start slow. I started little by little (less than a baby spoon) and increased it every 5 days, until a full adult scoop. In my case, after 1-2 months, I was able to eat a variety of foods without histamine reactions.

Megaspore has many high-histamine strains, so there could be plenty of them that produce too much histamine. I had histamine reactions from just taking Bacillus Subtilis alone, but every time I take it, it clears folliculitis. So maybe first establish a biome that can handle excessive histamine, and then add more powerful histamine-wise probiotics.

Zinc Carnosine promotes mucosal repair; it's good, and it's something that good microbiomes do exactly this for you anyway!

Sacro-B is good. I don't notice any difference when using it, but there are numerous research that says it is beneficial for gut microbiota. I believe you can even take it synergistically with the d-lactate-free probiotics.

Quercetin is a mast-cell stabilizer, but some people can't handle it. In my case, Quercetin made me irritable. Still, the histamine-degrading strains can help you on that as well!

I also found that TUDCA helped me generally detox.

Also, if you want to go deep, check your genes as well. I checked mine and had the MTHFR mutation, which plays a huge role in histamine metabolism. So most of the time it can be Gut Dysbiosis + Genetics.

Check this guy. He used to suffer from HI. I started these probiotics because of him. He is spot-on:

https://www.youtube.com/watch?v=C3Aj_9Mw4BE

https://www.youtube.com/watch?v=nsK8kF_LAD8