There are herbs that can be helpful in treating allergies (such as butterbur). Anaphylaxis, though, is a whole different ballgame:

"Anaphylaxis is a severe, potentially life-threatening allergic reaction. It can occur within seconds or minutes of exposure to something you're allergic to, such as the venom from a bee sting or a peanut.

The flood of chemicals released by your immune system during anaphylaxis can cause you to go into shock; your blood pressure drops suddenly and your airways narrow, blocking normal breathing. Signs and symptoms of anaphylaxis include a rapid, weak pulse, skin rash, and nausea and vomiting. Common triggers of anaphylaxis include certain foods, some medications, insect venom and latex.

Anaphylaxis requires an immediate trip to the emergency room and an injection of epinephrine. If anaphylaxis isn't treated right away, it can lead to unconsciousness or even death."

It's possible that herbal extracts might someday be found an effective part of treating anaphylaxis. Right now, though, if these symptoms occur it's serious business and requires immediate effective treatment (i.e. epinephrine, oxygen, injected antihistamines etc.) at an emergency room.
Some people who know they're at risk carry an epinephrine injection device to treat the initial onset of symptoms and give them the time they may need to reach professional care.

Here is a link that might be useful: Anaphylaxis

Yes, anaphylaxis is like a severe asthma attack - it is life threatening and needs immediate attention. Prevention is worth considering, but does not substitute for treatment when an attack occurs.

I think there will be herbal IL-33 inhibitors recognized. Right now, the total number of studies that even mention IL-33 is only 82. The first reference to IL-33 I saw is from 2005, and most of the research is within the last two years. I haven't seen anything in those studies that considered herbs.

One angle of investigation: IL-33 is a potent mast cell activator. These are immune cells that release little bomb packets of histamine, serotonin, and other chemicals that are involved in allergic reactions (anaphylaxis can be considered a special case of severe allergic reaction, where a large number of mast cells decide to carpet bomb indiscriminately).

The interleukins do not act in isolation - administer one, and it will have complicated effects on the others.

Some herbs of interest for preventing anaphylaxis include:
Albizzia lebbeck
Alpinia oxyphylla
Angellica
Cloves (eugenol)
Genistein
Licorice (Liquiritigenin and 18beta-glycyrrhetinic acid)
Green tea catechins
Magnolia officinalis
Mentha arvensis
Peony root, moutan
Picrorhiza kurroa
Rhus javanica
Silibinin (thistle seed)
Diet high in alpha-linolate (high in n-3 fats, low n-6 fats)