Influence of Hygroscopic Agents of Irritation

Influence of Hygroscopic Agents of Irritation From Cigarette Smoke, as Related to the Oral Cavity


St. Paul, Minn.

                With the great prevalence of smoking, it is most surprising on a search of the literature to find but little definite information dealing with its physiological effects. So far as the medical and dental professions are concerned, any advice given as to smoking habits of patients must be based primarily on unsupported personal opinion.

Physiologically the influence of smoking may be divided into two parts; (a) systemic, and (b) local. The dental profession is interested mainly in the local influence and its effect upon the oral mucosa and this discussion will deal solely with this phase.

The main local effect of smoking is that of irritation. The entire upper respiratory tract is subject to any irritants which may be present in smoke, and so far as the dentists are concerned, the oral cavity is of prime interest.

In the manufacture of cigarettes it is common practice to add a hygroscopic agent, a material which by virtue of its physical properties has a tendency to retain moisture or absorb it from the air. Its function is to keep cigarettes moist –that is fresh –after manufacture and until consumed. For this purpose glycerine, until recently, has been used exclusively.

On first consideration it would not seem that glycerine, so widely used for its soothing properties, could have any harmful effects. In cigarettes, however, we are not concerned with glycerine as such, but with its products of combustion, among which is a substance notorious for its irritant properties.

Glycerine is a three-carbon trihydroxy alcohol, and chemically among its products of combustion it is known to produce acrolein, a three-carbon unsaturated aldehyde. Believing that glycerine, on combustion, is a source of irritation, a new hygroscopic agent –diethylene glycol –was suggested. This substance has all the desirable hygroscopic qualities but due to its chemical constitution will not on combustion produce acrolein. Whether cigarettes treated with diethylene glycol would actually result in lesser irritating smoke could only be determined by investigation.

Mulinos, in a report of a research on the irritant properties of cigarette smoke as influenced by hygroscopic agents said,

“it is obvious that the cigarettes which had been made with diethylene glycol as hygroscopic agent proved to be less irritating that those with no hygroscopic agent and much less irritating than those with glycerine.”

Mulinos further reported that not only was the irritation less, but it lasted a shorter time. He said,

“The edema produced by the smoke solution from the untreated cigarette lasted an average of 31 minutes (8 to 82); that from the diethylene glycol lasted 8 minutes (0 to 21); and that with the glycerine lasted 45 minutes (17 to 122).”

Based upon these findings the conclusion may be reached that the substitution of diethy glycol for glycerine results in less irritation.

The method used by Mulinos was to smoke a cigarette with a mechanical smoker, passing the products of combustion through a small amount of water or some other absorbent liquid. A couple of drops of this solution was then instilled into the conjunctival sac of a rabbit. The degree of edema produced was taken as a measure of the irritant properties of the smoke.

The findings reported by Mulinos and confirmed by Wallace, Reinhard & Osborne were the result of work done on the eye of a rabbit. That these findings are applicable to the mucous membrane of the upper respiratory tract of smokers is evidenced by the work of Flinn. Flinn reported a series of clinical investigations conducted on smokers whose customary cigarette was glycerines treated, and who were suffering from congestion of some portion of the upper respiratory tract. He found that on smoking diethylene glycol treated cigarettes, in the majority of cases the congestion cleared completely; in all cases there was definite improvement. A further report by Flinn in the same journal gave corroboration to his original report.

It has been shown that there is a difference in the irritant properties of cigarette smoke, dependent upon whether glycerine or diethylene glycol is used as the hygroscopic agent –less for diethylene glycol than for glycerine –and it has further been shown that this difference in irritant properties is of a magnitude sufficient to affect the mucous membrane of the upper respiratory tract.

The dental profession, whose prime interest is the condition of the oral cavity, should be interested in this proved superiority of diethylene glycol treated cigarettes. In the normal mouth the instance of gingivitus is very high. Anything introduced into the mouth of an irritating character will accentuate this condition. The fact that diethylene glycol treated cigarettes are less irritating should indicate their value. It is common practice in the treatment of Vincent’s angina to prohibit smoking. This is natural, in that any irritant will aggravate the condition. Patients are often instructed to refrain from smoking, but it is often difficult to make them follow the advice. Under such circumstances it should be of great benefit to be able to advise such patients that if they must smoke, to smoke a cigarette proved definitely less irritating. Although Vincent’s angina and other mouth infections are not caused by smoking, yet unquestionable irritation to the gums, tongue, cheeks, etc., causes some degree of congestion and opens a possible avenue of infection.

With these considerations in mind, it should be worth while for the dental profession to know that diethylene glycol treated cigarettes are less irritating to the mucous membrane of the upper respiratory tract and more specifically to the oral cavity.


            Proc. Soc. exp. Biol. and Med., 1934, 32, 241-245.

Laryngoscope, Feb. 1935, Vol. XLV, No. 2, 149-154.

N.Y State Jour. Med., Vol. 35, No. 11, 590.

Arch. Otolaryngology, March 1936, Vol. 23, No. 3, 306-309.

Laryngoscope, Jan. 1937, Vol. XLVII, No. 1,  58-60.