There exists within the population subsets of individuals who display heightened skin reactivity to materials the majority find tolerable. In a series of investigations, we have examined interrelationships between many of the endpoints associated with the term 'sensitive skin'. In the most recent work, 58 volunteers were treated with 10% lactic acid, 50% ethanol, 0.5% menthol and 1.0% capsaicin on the nasolabial fold, unoccluded, with sensory reactions recorded at 2.5 min, 5 min and 8 min after application. Urticant susceptibility was evaluated with 1 m benzoic acid and 125 mM trans-cinnamic acid applied to the volar forearm for 20 min. A 2 x 23-h patch test was also conducted using 0.1% and 0.3% sodium dodecyl sulfate, 0.3% and 0.6% cocamidopropyl betaine and 0.1% and 0.2% benzalkonium chloride to determine irritant susceptibility. As found in previous studies, increased susceptibility to one endpoint was not predictive of sensitivity to another. In our experience, nasolabial stinging was a poor predictor of general skin sensitivity. Nevertheless, it may be possible to identify in the normal population individuals who, coincidentally, are more generally sensitive to a range of non-immunologic adverse skin reactions. Whether such individuals are those who experience problems with skin care products remains to be addressed.

Chemicals may possess a number of hazards to human health including the ability to cause skin irritation and contact allergy. Identification and characterization of these properties should fall within predictive toxicology, but information derived from human exposure, including clinical experience, is also of importance. In this context, it is of interest to review the case of benzalkonium chloride, a cationic surfactant. This chemical is a well-known skin irritant, but on occasions it has also been reported to have allergenic properties, typically on the basis of positive diagnostic patch test data. Because the accumulated knowledge concerning the properties of a chemical is employed as the basis for its regulatory classification (e.g. in Europe), as well as for informing the clinical community with respect to the diagnosis of irritant versus allergic contact dermatitis (ACD), it is important to distinguish properly which chemicals are simply irritants from those which are both irritant and allergenic on skin. A review of the information on benzalkonium chloride confirms that it is a significant skin irritant. However, both predictive test results and clinical data lead to the conclusion that benzalkonium chloride is, at most, an extremely rare allergen, except perhaps in the eye, but with many supposed cases of ACD being likely to arise from the misinterpretation of patch test data. As a consequence, this substance should not normally be regarded as, or classified as, a significant skin sensitizer.

The results confirm observations that rabbits overpredict skin effects in humans. Therefore, when validating in vitro methods, all available information, including human data, should be taken into account before making conclusions about their predictive capacity.

SACSouth American camelids IM Intramuscularly IV Intravenously O titis media has been reported in S AC but, unlike in dogs where it is usually an extension of otitis externa, it is said to occur more commonly as a sequel to upper re s p i r atory disease. [1][2][3][4] The clinical signs of otitis media in SAC are reported to be similar to those in dogs. 1 -4 Bro a d -s p e c t ru m antimicrobials, nonsteroidal anti-inflamm a t o ry drugs and support i ve care have been recommended as treatment, but the results of treatment have not been d o c u m e n t e d . 1 Total ear canal ablation and bulla osteotomy are re c o m m e n d e d for dogs with end-stage otitis externa and otitis media. 3 , 4 In this article we describe total ear canal ablation and lateral bulla osteotomy in an alpaca for otitis media that was re f r a c t o ry to conservative treatment. Case repor tA 4-year-old female alpaca with a 2month-old cria was re f e r red with a h i s t o ry of having suppurative otitis externa secondary to a migrating barley awn. Treatment had consisted of enrofloxacin (5 mg/kg IM once daily for 3 weeks) and intermittent flushing of the external acoustic meatus with isotonic saline solution to remove debris. The amount of discharge had decreased when the alpaca was re f e r red but it had developed neurological signs. [1][2][3][4] At presentation, the alpaca had a head tilt to the left, a flaccid left ear and lip and deviation of the muzzle to the right suggesting left facial nerve invo l ve m e n t ( Figure 1). The alpaca was assessed to be deaf in the left ear. The left eye showed miosis and ptosis and the globe was retracted when the alpaca tried to blink, a l l owing the third eyelid to adva n c e a c ross the cornea. The third eyelid was not prolapsed and no exposure keratitis was noted. The right side of the face was normal. Findings on physical examination were otherwise normal.Based on the progression of neurological signs despite antimicrobial therapy, radiographic assessment of the tympanic bullae was recommended, with a view to p roceeding with total ear canal ablation and lateral bulla osteotomy of the affected side. A 16-gauge 8.75 cm overthe-needle catheter was placed in the left jugular vein. The alpaca was sedated with xylazine (0.1 mg/kg IV) and anaesthesia was induced with ketamine (1 mg/k g I V), guaiphenesin (4 mg/kg IV) and diazepam (0.5 mg/kg IV) given to effect. An endotracheal tube was inserted with the animal maintained in sternal recumb e n c y, the cuff was inflated and anaesthesia was maintained with isoflurane in oxygen. The alpaca was placed in right lateral recumbency and flunixin meglumine (1 mg/kg IV) was administere d . Lateral and dorsoventral and oblique radiographs of the tympanic bullae re vealed sclerosis of the temporal bone of the tympanic bulla and narrowing of the lumen of the external acoustic meatus on the left side when compare d to the right. Otoscopic examination was i n c o n c l u s i ve because of the long and n a r row lumen of the external acoustic meatus in alpacas....

Subjective effects such as stinging, itching and burning commonly occur in the absence of any visible irritation and give rise to discomfort, which may be enough to deter an individual from using even the most effective of skin care products. The purpose of this study was to evaluate the sensitivity of different anatomical regions of the face to determine which region displayed the most intense stinging response to the application of lactic acid. The effect of occlusion on the level of response was also investigated. 45 volunteers were treated with 10% lactic acid on the nasolabial fold, forehead, chin and cheek, occluded and unoccluded for 8 min. Sensory reactions were recorded at 2.5, 5 and 8 min. The response levels on the occluded sites were always significantly lower than on the unoccluded sites, despite the dose per unit area being comparable. Females showed a trend towards being more sensitive to the subjective effects elicited by lactic acid than males, but these results were not conclusive. Interestingly, there was not a complete correlation between individuals who reacted on the nasolabial fold and the other sites, particularly the forehead. A positive stinging response on the nasolabial fold may not necessarily predict subjective responses to a product when used on other areas of the face.