Why does my throat feel bitter after putting in eye drops?

Audit expert: Liu Dongbao

Chief Physician of Ophthalmology Department, Shenyang Red Cross Hospital

Mobile phones, computers, books... As a modern person living in the 21st century, we spend more and more time using our eyes at close range every day, and anti-fatigue eye drops have become a "must-have medicine" in many people's homes.

In addition to relieving visual fatigue, eye drops are also one of the most common drug dosage forms in ophthalmology. Due to their direct and rapid effects, they are often used in the treatment of various eye diseases.

Source: israel21c.org

However, many people will encounter such a strange phenomenon when using eye drops: the drops are clearly in the eyes, but why do they feel bitter in the throat after a while? Is it a psychological effect or did the eye drops really flow into the mouth? Today, the editor will answer this question for you.

1How does bitterness come about?

Taste is a sense of flavor in humans and animals. All the flavors we can taste are composed of the five basic tastes of salty, sour, sweet, bitter and fresh. The process of taste generation Source: kids.frontiersin.org

The production of each basic taste involves a series of energy conversion and signal transduction processes. Taking bitterness as an example, after the substance that causes bitterness binds to the receptors on the surface of the taste receptor, it triggers a change in the cell membrane potential, which in turn prompts the taste cells to release neurotransmitters, which act on the primary afferent fibers of the taste and transmit the taste information to the central nervous system, thus producing the taste sensation of "bitter". (a) Schematic diagram of the taste bud structure (b) Microscopic image of the tongue surface Source: socialsci.libretexts.org

Taste receptors, also known as taste buds, are mainly distributed on the back of the tongue and the edge of the tongue, and a small number are scattered on the surface of the oral and pharyngeal mucosa. They are composed of taste cells and supporting cells. Cilia, also known as "taste hairs", grow on the top of taste cells. They extend from the holes on the surface of taste buds and are exposed inside the mouth. They are surrounded by abundant sensory nerve endings and are the key parts of taste perception.

Therefore, the common saying "tasting the flavor" is indeed in line with certain medical principles, that is, the flavorful substance must first enter the mouth before the human body can further feel its taste.

2Why do eye drops get into the throat?

It is now known that the first step in producing taste is for flavorful substances to come into contact with the taste buds.

So, how do the eye drops we put into the eyes "meet" the taste buds located in the mouth and pharynx, making people "taste" bitter?

Regarding this question, we need to start with the anatomical structure of the eye.

In anatomy, what we call "eye" in daily life is composed of two major parts: the eyeball and the accessory eye organs. The accessory eye organs include eyelids, conjunctiva, lacrimal apparatus, extraocular muscles and other structures, which can protect, move and support the eyeball.

Schematic diagram of lacrimal apparatus anatomy Source: Systematic Anatomy, 9th Edition

People's Medical Publishing House The lacrimal apparatus is composed of the lacrimal gland and the lacrimal duct. The human eye continuously secretes tears, which are evenly spread on the surface of the eyeball through blinking, preventing the cornea from drying out, washing away dust and sterilizing.

During this process, excess tears flow into the tear lake at the inner canthus, then pass through the lacrimal puncta and lacrimal canaliculi into the lacrimal sac, and then into the nasal cavity through the nasolacrimal duct.

Once the tear duct becomes narrow or blocked, the tears in the eyes cannot be drained normally. Over time, the composition of the tears, the number and proportion of bacteria will change. If the eyeballs are immersed in "deteriorated" tears for a long time, not only will epiphora occur, causing inconvenience to life, but the risk of eye diseases such as conjunctivitis and keratitis will increase, which requires timely treatment with medication or surgery.

From this we can see that the lacrimal duct, which connects the inner corner of the eye and the nasal cavity, is quite important.

When we put eye drops in our eyes, the eye drops will also enter the nasal cavity along this "channel". Since the nasal cavity and oral cavity are connected in the nasopharynx, the eye drops will also enter the oral cavity from the nasal cavity.

At this time, if the eye drops contain substances that can cause bitterness, the human body will naturally feel the bitterness. In other words, the bitterness in the throat after applying eye drops is indeed because the eye drops have been "eaten".

3Can eye drops still be used safely ?

I believe that seeing this, many friends will ask, will eye drops leave the original site of action and enter the mouth, will it cause harm to our body? For this point, you can rest assured that when using eye drops, it is normal for a small amount of medicine to enter the mouth, which usually does not cause harm to the body or cause poisoning reactions. Since the drug concentration of eye drops is generally low, it is unlikely to irritate the oral and gastric mucosa and cause serious side effects. However, for some eye drops with special effects, such as atropine, pilocarpine, timolol, etc., which may act on other systems of the human body and cause adverse reactions, everyone must read the instructions carefully before using them , especially for special groups such as pregnant women, lactating women, newborns and premature babies, special attention must be paid to the contraindications of drug use to avoid serious adverse consequences.

How to use eye drops Source: ranelle.com

In addition, before applying the medicine, gently pull down the lower eyelid, drop the eye drops into the conjunctival sac below, gently close the eyes for a few minutes and press the lacrimal sac . This can not only effectively reduce the excretion of drugs from the tear duct and increase the absorption of the eyes, but also reduce the occurrence of systemic adverse reactions.

In addition, when multiple eye drops are needed for treatment, the interval between different eye drops should not be less than 5 minutes to avoid interference between different medicines and affect their efficacy.
Although it is normal to feel a bitter taste in the mouth after using eye drops, the editor still wants to remind everyone that if the discomfort after use is too strong or other adverse reactions occur, you should see a doctor as soon as possible and let the doctor decide whether you can continue to use it.