What is that
Antihistamine eye drops is a medicine for ocular use, formulated with active ingredients with an antihistamine and antiallergic action.
Indications
What is Antihistamine Eye Drops used for?
Antihistamine eye drops are indicated for the treatment of allergic states affecting the eye. More in detail, the use of antihistamine eye drops is useful to counter the typical symptoms of conjunctivitis and keratoconjunctivitis of an allergic nature, such as inflammation, itching, redness, swelling, burning and photosensitivity.
Please note
The antihistamine eye drops are not able to cure allergies, but they keep under control the symptoms that are triggered after the allergic reaction, attenuating and contrasting them.
Composition
Active Ingredients contained in the Antihistamine Eye Drops
An antihistamine eye drops contains active ingredients with an antihistamine and antiallergic action which - acting directly on the mechanisms underlying the allergic reaction - counteract the typical symptomatology.
Among the active ingredients most used, we recall:
- Tonzilamina (Collirio Alfa® Antihistamine, Imidazyl® Antihistamine): is an active antihistamine that works by blocking H1 receptors for histamine. Consequently, this neurotransmitter - widely involved in the onset of allergic reactions - is no longer able to interact with its own receptors and to exercise its role in the onset of symptoms.
- Pheniramine (Tetramil®): is another active antihistamine, which acts by blocking H1 receptors for histamine.
- Spaglumic acid (Naaxia®): also known as N-acetylaspartyl-glutamic acid, spaglumic acid is an active ingredient with an antiallergic action that is performed through the inhibition of mast cell degranulation and the consequent release of histamine.
In addition to the active ingredients with antihistamine and anti-allergic activity, active ingredients with decongestant action can also be present in an antihistamine eye drop which - thanks to their activity - helps restore the physiological conditions of the ocular mucosa. Among these active ingredients, we recall:
- Naphazoline (Collirio Alfa® Antihistamine, Imidazyl® Antihistamine): is a sympathomimetic active ingredient endowed with agonist activity against α1-type adrenergic receptors. Thanks to this particular activity, naphazoline is able to exert a local vasoconstrictor action, favoring the decongestion of the conjunctival mucosa.
- Tetrizoline (Tetramil®): is another active ingredient able to exert a decongestant action by activating α1-type adrenergic receptors.
Features
What Features Should an Antihistamine Eye Drops Have?
An antihistamine eye drops, like any other type of eye drops, must have very specific characteristics in order to be used safely at an ocular level. Among the most important characteristics that similar medicines must possess, we remember:
- Infertility : since the eye is a particularly delicate region and has fewer defenses than other body areas, it is of fundamental importance that the eye drops are sterile.
- A physiological pH : in order to avoid side effects such as burning and discomfort, the antihistamine eye drops, when possible, should have a pH similar to that of the tear fluid (indicatively, around 7.4).
- The isotonia : as important as the pH in order to avoid the occurrence of secondary effects is the isotonia of the antihistamine eye drops. In fact, it should have a tonicity equal to that of a 0.9% sodium chloride solution (ie, equal to the so-called saline solution).
dosage
How much eye drops must I take and for how long?
The dosage of an antihistamine eye drop may vary depending on the medicinal product used. However, usually, it is necessary to instill one or two drops of the drug in the eye, from two to four times a day.
Please note
Although many antihistamine eye drops can be dispensed without a prescription, their use should only be done with the advice of a doctor.
In particular, if an antihistamine eye drops also contains decongestants with sympathomimetic action, its use should not exceed 3-4 days. This is because an improper and inordinate use of similar active ingredients can cause a paradoxical effect whereby the conjunctival mucosa becomes further congested.
Mode of use
How to apply the antihistamine eye drops?
Antihistamine eye drops apply in the same way as all other eye drops:
- Before proceeding with the installation of the product it is necessary to wash your hands thoroughly.
- The instillation of the drops of antihistamine drops should be carried out by tilting the head backwards and lightly pulling the lower eyelid to facilitate the entry of the product into the eye. During drug administration, it is very important that the spout of the container does not come into contact with the eye and / or eyelid.
- At the end of the application of the eye drops, the eyes can be closed for a few seconds, preferably not too abruptly.
In case of contact lens wearers, these should be removed before the drug is given and can be reapplied after about 15-20 minutes. However, in case of doubt, it is advisable to ask your doctor or eye specialist for advice.
Side effects
The type and intensity of the side effects induced by an antihistamine eye drop may vary depending on the active ingredients contained in the medicine and on the sensitivity of each patient to the same drug.
However, among the main side effects that can occur, we recall:
- Transient burning;
- Feeling of annoyance;
- Transient increase in lacrimation;
- Hypersensitivity (a rather rare event, but not impossible).
Furthermore, the appearance of side effects caused by the systemic absorption of the active ingredient (a rare occurrence) cannot be excluded.
Finally, it is good to remember that an antihistamine eye drop containing also decongestants with sympathomimetic action could cause the appearance of secondary effects such as dilation of the pupil and increase in intra-ocular pressure.
Pregnancy and breastfeeding
The use of an antihistamine eye drops during pregnancy and lactation is not always recommended. This depends substantially on the active ingredient used. Therefore, pregnant women and breastfeeding mothers, before taking any type of antihistamine eye drops, should seek the advice of their doctor.
Contraindications
The use of antihistamine eye drops is contraindicated in case of known hypersensitivity to any of the substances contained in it (active ingredients or excipients).
If the antihistamine eye drops contain decongestants with sympathomimetic action, its use is contraindicated also in the following cases:
- In the presence of glaucoma or other serious eye diseases;
- In the case of concomitant therapy with monoamine oxidase inhibitors, as severe hypotensive crises may occur.
