Understanding Allergy Medicines: Histamine, the Autonomic Nervous System, and Kampo Medicines August 5, 2026 (Wednesday) Reiwa8

Today, I studied Chapter 3 of the Registered Salesperson Examination textbook, "Main Medicines and Their Effects."  
The topics were oral allergy medicines, oral medicines for rhinitis, and Kampo (traditional Japanese herbal) formulations.

At first, words such as histamine, receptors, the sympathetic nervous system, the parasympathetic nervous system, and anticholinergic ingredients felt like a completely different language.

However, by organizing each concept step by step, I began to understand how allergic symptoms occur and how medicines work.

When an allergen such as pollen or food enters the body, an immune reaction occurs.

The immune system stimulates mast cells, and these cells release substances such as histamine.

Histamine then binds to receptors and causes symptoms such as:

- Blood vessel dilation
- Increased vascular permeability
- Sneezing
- Runny nose
- Itching

Antihistamine ingredients such as chlorpheniramine maleate and mequitazine do not remove histamine itself.

Instead, they prevent histamine from binding to its receptors and reduce allergic symptoms.

Some antihistamine ingredients also have anticholinergic effects. Therefore, side effects such as:

- Dry mouth
- Constipation
- Difficulty urinating

may occur.

I also learned that the autonomic nervous system plays an important role in rhinitis medicines.

Pseudoephedrine hydrochloride is an adrenergic ingredient that stimulates the sympathetic nervous system.

The sympathetic nervous system is the "fight-or-flight" system that prepares the body for activity and stress.

When it is stimulated:

- Blood vessels in the nasal mucosa constrict.
- Swelling and congestion decrease.
- Nasal blockage improves.

On the other hand, belladonna alkaloids are anticholinergic ingredients.

They block the action of acetylcholine, a neurotransmitter of the parasympathetic nervous system.

As a result, mucus secretion decreases, helping to reduce a runny nose and sneezing.

Although many medicines are used for nasal allergy symptoms, they work in different ways:

- Some block histamine.
- Some stimulate the sympathetic nervous system.
- Some suppress parasympathetic nervous system activity.

I learned that understanding where and how each medicine works is more important than simply memorizing names.

I also studied Kampo formulations used for allergy symptoms.

In Kampo medicine, treatment is selected according to both the person's constitution and symptoms.

Examples of Kampo medicines mainly used for skin symptoms include:

- Shofusan
- Jumihaidokuto
- Tokiinshi
- Inchinkoto

Examples of Kampo medicines mainly used for nasal symptoms include:

- Kakkonto-ka-senkyushin'i
- Shoseiryuto
- Shin'i-seihaito

In particular, Shin'i (Magnolia flower bud) is a crude drug often used for nasal congestion and rhinitis. It appeared several times during today's study.

I also learned about licorice (Kanzo).

Glycyrrhizin, a component of licorice, has anti-inflammatory effects, but long-term use may cause pseudoaldosteronism.

Possible symptoms include:

- Swelling
- Increased blood pressure
- Low potassium levels
- Muscle weakness

Today's study reminded me that medicines cannot be understood by memorizing names alone.

It is important to think about:

"What causes the symptoms?"
"Where does the medicine act?"
"Why do side effects occur?"

Even though many medical terms and Kampo names are difficult, step-by-step learning gradually leads to better understanding.

I would like to continue building on today's knowledge as I prepare for the Registered Salesperson Examination.

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