TOXICOLOGY AND APPLIED PHARMACOLOGY i', 559-565 (1965) 

Comparative Acute Effects of Some Chemicals 

on the Skin of Rabbits and Guinea Pigs’ 

ROBERT L. ROUDABUSH, C. J. TERHAAR, DAVID W. FASSETT, 

AND STANLEY P. DZIUBA 

Laboratory of Industrial Medicine, Eastman Kodak Company, Rochester, Sew York 

Received April lb, 1964 

The potential hazard of human skin contact with a chemical is frequently determined from data obtained from the application of the chemical to the skin of experimental animals. Exposures of this type permit one to evaluate both the type and 

degree of dermal reaction as well as the possibility of percutaneous absorption. The 

literature records examples of the use of a number of mammalian species for such 

studies. However, since the publication of Draize et al. (1944)) and the subsequent 

designation of the rabbit as the sole animal species recognized for such tests in the 

regulations under the Federal Hazardous Substances Labeling Act (21 CFR 191; 

hereinafter referred to as the “Regulations”), industrial toxicologists in the United 

States have restricted themselves largely to this single species for the routine screening of skin effects caused by chemicals or chemical formulations. 

While the rabbit has been useful in predicting human response to skin irritants or 

penetrants, there has apparently been little inclination to carry out systematic comparisons with other species. For the past fifteen years, this laboratory has used the 

“albino” guinea pig for studies of skin irritation, percutaneous absorption, and skin 

sensitization. Some of the advantages of the guinea pig are obvious; namely, lower 

animal cost and food consumption, lesser space requirement, ease of handling, and, 

especially, the possibility of testing chemicals of which only limited amounts are 

available. Over the years the dermal effects of a large number of organic compounds 

of extremely diverse types, including most commonly used industrial chemicals, have 

been tested in this species. Many of these data can be found in the recent revision 

of Patty’s book (1962). Since our experience with skin tests on the intact abdomen 

of guinea pigs has shown this species to be very useful for such studies, it was felt 

that it would be of interest to compare the reactions of the guinea pig with those of 

the rabbit to materials of various types of toxic action and potency. Substances in 

common use in industry were included in this study as well as some household substances. 

MATERIALS AND METHODS 

All of the guinea pigs used in this study were males, Hartley derived,” ranging in 

weight from 400 to 900 g. The white rabbits were of both sexes, were purchased from 

a local supplier, and varied from 1 to 4 kg in weight. 

1 Presented at the Third Annual Meeting of the Society of Toxicology, Williamsburg, Virginia, 

March 9-11, 1964. 

zz Tumblebrook Farms, Brant Lake, New York. 

559 
560 ROBERT L. ROUDABUSH ET AL. 

The hair was removed from the test area of all animals by clipping. The guinea 

pigs had the hair stubble removed with a barium sulfide depilatory which was allowed 

to remain on the skin for only a few minutes. After this, the skin was washed in 

running water and the animals were allowed to dry for several hours before application of the test materials. For the abraded skin tests, abrasions were made longitudinally every 2-3 cm by drawin g a harpoon-shaped needle over the skin with 

sufficient pressure to penetrate only the stratum corneum. 

Acute dermal toxicity. The procedure for testing acute dermal toxicity on rabbit 

skin was that described in the Regulations (21 CFR 191.10). The only exceptions 

to this procedure were that the animals were not immobilized for 24 hours but were 

confined to cages, and the skin of all rabbits was abraded. A minimum of 3 dosages 

was employed, usually with 4 animals per dosage, and the LDoo was calculated by 

the method of Finney (1952). Rubber dental dam was used as the sleeve material 

except with those materials that react with rubber, in which case S-mil fluorocarbon 

plastic sheeting was used. 

The test compounds were applied undiluted to guinea pigs on a l-inch square 

cellulose pad3 held onto the clipped and depilated intact abdomens or the clipped 

and depilated abraded backs under a cuff of rubber dental dam or plastic sheeting 

as necessary. The edges of the cuff were sealed by attaching them to the skin with 

black rayon tape,” one side of which was coated with adhesive. The number of 

dosages, animals per dosage, and the method of calculation of the LDSo were the same 

as with rabbits. 

Primary irritation. The procedure for testing and evaluating primary irritation was 

identical to that described in the Regulations (2 1 CFR 191.1 I), except that the 

rabbits were not immobilized and the l-inch square cellulose pads were used instead 

of surgical gauze. Each compound was applied to 6 rabbits with intact, and 6 with 

abraded, skin. 

The test procedure in the guinea pig included application of the materials, or 

aqueous solutions of them, on cellulose pads held in contact with the skin under an 

appropriate sleeve. Six guinea pigs with clipped, depilated, intact abdomens and 6 

with clipped, depilated, abraded backs were used for each material. 

Calculations of the primary irritation score were made according to the Regulations (21 CFR 191.11). However, when intact or abraded skin was evaluated alone, 

the average values at 24 and 72 hours were divided by 2 instead of 4. 

The identity, source, and quantity of the test substances applied to the animals 

are listed in Table 1. 

Acute Dermal Toxicity 

RESULTS 

Table 2 lists the LD6,,‘s obtained as a result of the acute dermal toxicity studies. 

Benzene, carbon tetrachloride, and acetone, all compounds which are “practically nontoxic” by skin contact according to the system of classification of Hodge and Sterner 

(1949), gave similar responses regardless of whether intact guinea pig abdomen, 

3 Multilith pads for Multilith masters, Addressograph-Multigraph Corporation, Cleveland, 

Ohio. 

4 Eastman Kodak Company, Rochester, New York. 
SKIN OF RABBITS AND GUINEA PIGS 561 

TABLE 1 

DOSE AND SOURCE OF SUBSTANCES USED IN PRIMARY IRRITATION TESTS 

Compound Dose and concentration Source 

Acetic acid 0.5 ml, 4% in water (v/v) 

Ammonia. household 0.5 ml, undiluted 

Borax 10 ml, 5% in water (w/v) 

Boric acid 5 ml, 10% in water (w/v) 

2.Butanone 0.5 ml, undiluted 

Carbon tetrachloride 0.5 ml, undiluted 

Gasoline 0.5 ml, undiluted 

Kerosene 0.5 ml, undiluted 

Phenylhydrazine 50 mg, undiluted 

Sodium carbonate 2 ml, 257, in water (W/V) 

Sodium sulfite 2 ml, 25% in water (w/v) 

Sucrose 1 ml, 50% in water (w/v) 

Trisodium phosphate 2 ml, 25% in water (w/v) 

Water. distilled 0.5 ml 

Eastman Organic Chemical no. P763 

Grocery store 

Kodak Photographic Chemical 

Kodak Photographic Chemical 

Eastman Organic Chemical no. 383 

Eastman Organic Chemical no. P444 

Service station 

Service station 

Eastman Organic Chemical no. 329 

Kodak Photographic Chemical 

Kodak Photographic Chemical 

Grocery store 

Kodak Photographic Chemical 

Laboratory 

Compounds 

TABLE 2 

ACUTE DEFLMAL LD,, (ML/KG) OF TEST COMPOUNDS 

Rabbit, Guinea pig, 

Source” abraded skin intact skin 

Guinea pig, 

abraded skin 

Acetone 

Benzene 

Carbon tetrachloride 

Butylamine 

Aniline 

Rutoxyethanol 

Acrylonitrile 

Parathion 

P297 

P777 

P444 

1261 

25 

P2270 

P.5161 

- 

>9.4 

>9.4 

>9.4 

>1.5 

0.82 

0.68 

0.28 

0.07 

>9.4 >9.4 

>9.4 >9.4 

>9.4 >9.4 

0.58 >l.S 

1.29 2.15 

0.23 0.30 

0.46 0.84 

0.60 ,030 

a Numbers refer to Eastman Organic Chemicals sold by Distillation Products Industries, 

Rochester, New York. The parathion was a sample of 99.6% purity purchased from American 

Cyanamid Company, Wayne, New Jersey. 

abraded guinea pig back, or abraded rabbit skin was used. Butylamine, which quickly 

causes necrosis in contact with skin, appears much more toxic, based on the LD;,o’s, 

on intact guinea pig abdomen than on either abraded guinea pig or rabbit back. This 

circumstance is probably due to the fact that extensive and severe necrosis of the 

skin of the abdomen is more likely to lead to complications and death than necrosis 

over a larger area involving primarily the back. 

Aniline appears to be more toxic to rabbits than to guinea pigs regardless of the 

location of the application and the condition of the skin. However, aniline was more 

toxic when applied to the intact guinea pig abdomen than it was when applied to 

the abraded back. 

Butoxyethanol was less toxic to the rabbit than it was to the guinea pig by either 

type of contact, and, according to Hodge and Sterner’s (1949) classification, would 

be classed as “slightly toxic” to rabbits but “moderately toxic” to guinea pigs. 

Acrylonitrile, conversely, was more toxic to rabbits than it was by the same type 

of application to guinea pigs, while the LDao for guinea pigs with intact abdominal 

skin was between these two values. 
562 ROBERT L. ROUDABUSH ET AL. 

The intact guinea pig abdomen was more sensitive than the abraded back, giving 

lower LD50 values for all compounds for which a difference was demonstrated. This 

was not unexpected since previous experience had shown the abdominal skin to be a 

more responsive area. 

According to Deichmann et al. (1952), the dermal LDao of parathion to rabbits 

is 870 mg/kg, which is similar to our results with guinea pigs. Lehman (1948), on 

the other hand, reported the acute dermal LDjo for rabbits to be 40-50 mg/kg. Our 

results on rabbits agree more closely with those of Lehman than with those of Deichmann et al. 

Primary Irritation 

Table 3 summarizes the data collected from the primary irritation studies. Table 4 

lists the materials in descending order of irritancy according to type of test, together 

with some correlation coefficients suggested by Snedecor (1946). 

The average primary irritation scores listed in Table 3 reveal that the abraded 

rabbit skin was more sensitive to the irritant effects of all fourteen compounds than 

was the intact rabbit skin, while ,the intact guinea pig showed equal or greater irritation than the abraded guinea pig skin with twelve of these. Seven of the materials 

produced more irritation on intact guinea pig skin than on abraded rabbit skin. 

Thirteen compounds produced equal or greater irritation in the intact guinea pig 

skin test than in the intact rabbit skin test, and nine gave equal or greater scores in 

the intact guinea pig skin test than in the combination of abraded and intact rabbit 

skin. The ranking of compounds according to irritancy in both guinea pig tests is 

extremely well correlated with the rabbit test. 

DISCUSSION 

As pointed out above, of the eight compounds tested for acute dermal toxicity, 

three gave similar results in both the rabbit and intact guinea pig skin test. According to the classification system of Hodge and Sterner (1949), three compounds, 

butylamine, aniline, and acrylonitrile, would fall into the same class regardless of 

the test animal, the first two being “slightly toxic” and the third “moderately toxic.” 

Butoxyethanol and parathion were in different classes depending on the species, the 

former being “slightly toxic” to rabbits and “moderately toxic” to guinea pigs with 

intact skin, while the latter was just the reverse. 

According to the Regulations [ 21 CFR 191.1 (f) (3)], acetone, benzene, and 

carbon tetrachloride would not be classed as LLtoxic” by dermal application in either 

species. All the other five compounds would be classed as “toxic” by the intact guinea 

pig skin test, and four of the five “toxic” by the rabbit test. Parathion would be 

“highly toxic” by the rabbit test [ 2 1 CFR 191.1 (e) (3) ] . 

The differences in the LDsO’s calculated from the rabbit and the intact guinea pig 

skin tests are no greater than the differences frequently recorded for a chemical tested 

by two laboratories in a single species. The dermal LDBO’s for parathion as determined 

by Deichmann et al. (1952) and Lehman (1948) have been cited above as an example 

of such differences found in the same species. 

Since the Regulations [ 2 1 CFR 191.1 (g) (2) ] define a primary skin irritant as 

a material having an empirical score of 5 or more when tested on rabbits, none of the 
SKIN OF RABBITS AND GUINEA PIGS 563 

TABLE 3 

SUMMARY OF PRIMARY IRRITATION SCORES 

Compound 

Acetic acid, 

4% aqueous 

Ammonia, 

household 

Borax 

Boric acid 

2-Butanone 

Carbon 

tetrachloride 

Gasoline 

Kerosene 

Phenylhydrazine 

Sodium 

carbonate 

Sodium 

sulfite 

Sucrose 

Trisodium 

phosphate 

Water, 

distilled 

Animal 

Intact 

skin 

Abraded 

skin 

Intact plus 

abraded skina 

Rabbit 1.5 3.6 2.6 

Guinea pig 1.9 1.9 1.9 

Rabbit 3.2 5.0 4.1 

Guinea pig 5.6 5 .O 5.3 

Rabbit 1.6 2.3 2.0 

Guinea pig 1.5 1.4 1.4 

Rabbit 0.8 2.5 1.7 

Guinea pig 2.7 1.4 2.1 

Rabbit 0.8 2.7 1.8 

Guinea pig 1.6 2.4 2.0 

Rabbit 2.8 4.0 3.4 

Guinea pig 4.1 2.2 3.1 

Rabbit 2.0 2.9 2.4 

Guinea pig 3.9 2.8 3.3 

Rabbit 1.9 3.2 2.5 

Guinea pig 3.6 2.6 3.1 

Rabbit 1.8 3 .o 2.4 

Guinea pig 3.6 2.6 3.1 

Rabbit 2.1 5.0 3.5 

Guinea pig 2.1 2.6 2.3 

Rabbit 1.6 3.1 2.4 

Guinea pig 2.4 1.7 2.0 

Rabbit 0.4 2.3 1.4 

Guinea pig I.5 0.9 1.2 

Rabbit 3.4 5.1 4.2 

Guinea pig 6.3 5.1 5.7 

Rabbit 1.1 1.8 1.4 

Guinea pig 1.3 1.0 1.1 

Range Rabbit 0.4-3.4 1.8-5.1 1.4-t.2 

Guinea pig 1.3-6.3 0.9-5.1 1.1-5.7 

Average Rabbit 1.79 3.34 2.56 

Guinea pig 2.87 2.40 2.69 

Correlation coefficient to Rabbit 0.943 0.962 - 

rabbit, intact plus abraded Guinea pig 0.803 0.861 0.847 

0 The calculation of this primary irritation score is described in section 191.11 of the Regulations. In the other columns for intact or abraded skin the sum of the values at 24 and 72 hours 

was divided by 2 rather than 4. 

materials tested could be classed as irritants according to the results of our tests. 

However, household ammonia and trisodium phosphate would fall in the irritant class 

if the results of the guinea pig tests were calculated in the same manner as in the 

rabbit test. It is interesting also that these same results would have been obtained if 

only the intact guinea pig skin had been used in the test. 

The results of the comparisons made in this study indicate that the guinea pig skin 

test provides essentially the same information as the rabbit skin test. Thus, there 
Score 

Guinea pig, 

intact skin 

TABLE 4 

RANKING OF SUBSTANCFS ACCORDING TO IRRITANCY IN EACH TESTY 

Rabbit, Guinea pig, Rabbit, G

intact skin abraded skin abraded skin intact 

>4.09 

4.09-2.09 

Trisodium 

phosphate 

Ammonia 

Carbon 

tetrachloride 

Gasoline 

Kerosene 

Phenylhydrazine 

Boric acid 

Sodium sulfite 

Sodium carbonate 

- 

Trisodium 

phosphate 

Ammonia 

Carbon 

tetrachloride 

Sodium carbonate 

<2.09 

Spearman’s rank 

correlation 

coefficient to 

rabbit, intact 

plus abraded 

Acetic acid 

2-Butanone 

Borax 

Sucrose 

Water 

0.743 0.896 0.793 0.963 0.752 

Trisodium 

phosphate 

Ammonia 

Gasoline 

Kerosene 

Phenylhydrazine 

Sodium carbonate 

2-Butanone 

Carbon 

tetrachloride 

Gasoline 

Kerosene 

Phenylhydrazine 

Borax 

Sodium sulfite 

Acetic acid 

Water 

Boric acid 

2-Butanone 

Sucrose 

Acetic acid 

Sodium sulfite 

Boric acid 

Borax 

Water 

Sucrose 

Trisodium 

phosphate 

Ammonia 

Sodium 

carbonate 

Carbon 

tetrachloride 

Acetic acid 

Kerosene 

Sodium sulfite 

Phenylhydrazine 

Gasoline 

2-Butanone 

Boric acid 

Sucrose 

Borax 

Triso

p

Amm

Gas

Kero

Carb

te

Phen

Sodi

Boric 

Water 2-Bu

Sod

Acet

Bora

Sucr

Wate

a Braces group substances with identical primary irritation scores. 
SKIN OF RABBITS AND GUINEA PIGS 565 

is a sound basis for the use of the guinea pig as an alternate species to the rabbit for 

skin irritation and percutaneous absorption tests specified in governmental regulations, as well as for general use in industrial toxicology laboratories. 

SUMMARY 

A comparison was made between guinea pigs and rabbits in their response to various compounds 

in regard to acute dermal toxicity and primary irritation. 

Of the eight compounds tested for acute dermal toxicity, only one (parathion) would have been 

placed in a higher toxicity classification by the rabbit test than by the intact guinea pig skin test. 

The information obtained in the primary irritation tests showed that the intact guinea pig skin 

test is as sensitive as, or more sensitive than, the rabbit skin test in eliciting dermal reactions. 

It is concluded that the intact guinea pig skin test serves as a useful alternate for the rabbit 

test and that there is no scientific basis for preferring the rabbit as a test animal 

REFERENCES 

DEICHMANN, W. B., PUGLIESE, W., and Cnssm~, J. (1952). Effects of dimethyl and diethyl 

paranitrophenyl thiophosphate on experimental animals. .4.M.A. Arch. Ind. Hyg. Occupational 

Med. 5, 44-51. 

DRAIZE, J. H., WOODARD, G., and CALVERY, H. 0. (1944). Methods for the study of irritation and 

toxicity of substances applied topically to the skin and mucous membranes. J. Pharmacol. Exptl. 

Therap. 82, 377-390. 

FINNEY, D. J. (1952). Probit Analysis, 2nd ed., Chapter 3. Cambridge Univ. Press, London and 

New York. 

HODGE, H. C., and STERNER, J. H. (1949). Tabulation of toxicity classes. Am. Znd. Hyg. Assoc. 

Quart. 10, 93-96. 

LEHMAN, A. J. (1948). The toxicology of the newer agricultural chemicals. Quevt. Bull. Assoc. 

Food Drug Ofic. U.S. XII, 82-89. 

PATTY, F. A. (1962). Industrial Hygiene and Toxicology (David W. Fassett and Don D. Irish, 

eds.), 2nd ed., Vol. II. Wiley (Interscience), New York. 

SNEDECOR, G. W. (1946). Statistical Methods, 4th ed., pp. 164-167. Iowa State Univ. Press, 

Ames, Iowa.