ALLERGAN ® - Diphenhydramine

ALLERGAN ® is a hydrochloride Diphenhydramine drug

THERAPEUTIC GROUP: Antihistamine for topical use

IndicationsAction mechanismStudies and clinical effectiveness Usage and dosage instructionsWarnings Pregnancy and lactationInteractionsContraindicationsUndesirable effects

Indications ALLERGAN ® - Diphenhydramine

ALLERGAN ® is indicated for the topical symptomatic treatment of insect bites, sunburn or dermatitis with high pruritic activity.

Mechanism of action ALLERGAN ® - Diphenhydramine

ALLERGAN ® is an antihistamine based on diphenhydramine hydrochloride, antagonist of the first generation H1 receptor, particularly active at the skin level in inhibiting itching and dermatologic symptoms induced by histamine at the local level.

The competitive and reversible inhibitory action induced by Diphenhydramine with respect to H1 histamine receptors, controls the action of histamine at the local level, and in particular that of the endothelial cells that cover the small vessels, responsible for the impressive edemigenic activity of this inflammatory mediator, thus controlling the classic symptomatology that is observed in insect bites or following excessive exposure to ultraviolet rays.

The low systemic absorption that follows the topical use of this drug greatly limits the potential side effects of the therapy with first-generation antihistamines such as sedation and sleepiness.

Diphenhydramine is also attributed to the important antipruritic activity, which is certainly one of the most important goals of antihistamine therapy.

Studies carried out and clinical efficacy


Arch Pediatr Adolesc Med. 2006 Jul; 160 (7): 707-12.

Randomized double-blind study demonstrating the inability of diphenhydramine to improve nocturnal sleep in small children between the ages of 6 and 15 months, characterized by continuous awakenings and difficult sleep.


J Trauma. 1993 Mar; 34 (3): 354-7.

Interesting work that demonstrates the efficacy of diphenhydramine, thanks to both sedative and antiallergic activity, in favoring the recovery of minor skin lacerations through sutures.


Masui. 2012 Sep; 61 (9): 988-92.

Important work that demonstrates the efficacy of Diphenhydramine, for systemic use, in reducing post-operative vomiting in small patients undergoing laparoscopic surgery.

Method of use and dosage


Topical cream for 2 g of Diphenhydramine hydrochloride.

Doctors generally recommend applying a thin layer of cream 2 or 3 times a day directly on the region affected by the pathological process.

Warnings ALLERGAN ® - Diphenhydramine

Before using ALLERGAN ® it would be preferable in any case to consult your doctor with whom to assess the prescriptive appropriateness.

In order to optimize the success of the therapy, reducing the potential side effects would be appropriate:

  • Avoid the use of occlusive bandages, such as to increase the risk of sensitization;
  • Avoid applying the cream on particularly large areas of skin;
  • Avoid contact of the drug with torn skin and exposed mucous membranes.
  • Avoid exposure to ultraviolet radiation following the use of ALLERGAN ®.

It is also recommended to keep the drug out of the reach of children.


During pregnancy and in the subsequent period of breastfeeding it would be preferable to avoid the use of ALLERGAN ®, limiting it to cases of real need and clearly always under the strict supervision of your gynecologist.


Drug interactions worthy of clinical note are currently unknown.

Contraindications ALLERGAN ® - Diphenhydramine

The use of ALLERGAN ® is contraindicated in case of hypersensitivity to the active ingredient or to one of its excipients or to other structurally related molecules.

Undesirable effects - Side effects

The use of ALLERGAN ® especially when prolonged for a long time could cause the onset of burning, rash and photosensitivity.

Adverse reactions from hypersensitivity to the drug were decidedly more rare.


ALLERGAN ® is a non-prescription drug.