Effects of continuous lacrimation on the pathogenesis of dermatitis in rabbits

[POURPOSE] Rabbit is one of the species which is used in the toxicity study for dermal or instillation administration. In some instillation toxicity studies, we experienced dermatitis around the eye. To clarify the cause of the dermatitis, we examined the effects of continuous lacrimation. [METHOD] Lacrimal puncta of the left eye was obstructed using lacrimal punctal plug or handmade plug-like device in ten male NZW rabbits and observed for 4 weeks. [RESULTS AND DISCUSSION] The lacrimal punctal plug for human (OD 1.1mm) could not keep obstruction for long time, meanwhile a handmade plug-like device (OD 1.25 or 1.4mm) could sufficiently keep obstruction. All rabbits showed transient or continuous lacrimation during the observation period. Regardless of the presence of the protecting collar, alopecia was observed in 5 animals that showed continuous lacrimation. Scab formation in the area of alopecia was observed in 3 animals with collars, suggesting that the scab was formed by chafing with the corner of feeder. In the histopathology, inflammatory cell infiltration and dermatitis were observed in the area of alopecia. For the induction of the so-called “moist dermatitis” might require infection by bacteria, however, the present study indicated that the continuous lacrimation itself could induce alopecia and dermatitis around the eye. Therefore, in the toxicity studies using rabbits, an alopecia and dermatitis could be induced by the continuous lacrimation without administration of any toxic compound.