The redness of the skm, mostly combined with hyperidrosis, is generally considered an important symptom of influenza, and is interpreted as an angioneurosis (vasomotor paralysis) due to influenza toxins. We have remarked above that this hyperidrotic redness of the face, combined with spasmodic cough, forms an important point of differential diagnosis between the croupous influenza pneumonia and the genuine form.
Frequently the redness of the skin appears in the form of a marked scarlatiniform or measly eruption, particularly on the face, forehead, chest, and other parts of the trunk; frequently also on the upper extremities, more rarely on the lower. Very often the face shows a mottled redness, so that the external appearance of many patients, with their conjunctivitis, coryza, and cough, vividly reminds one of a case of measles, and that, although the eruption existing has the characters of the initial rash of scarlet fever-fine, flaky, closely aggregated, and not raised. Teissier describes a series of cases in which the differentiation between his "scarlatiniform" and "rubeolar " form of influenza and true scarlet fever or measles was difficult.
* " Par la vehemence de toux plusieurs femmes grosses acoucherent avant la terme" (Pasquier, 1410); "Abortions and death of childbed women were common" (Th. Short, 1517).
The above described measly and scarlatiniform erythemata, to which may be added urticaria (R. Guiteras's "influenza erythematosa"), occur most frequently during the initial stage and at the height of the disease; they are generally of short duration, sometimes very transitory, and are only occasionally followed by desquamation. It is not improbable that the scarlatiniform or measly eruption may often have been due to the influence of drugs, especially of antipyrin.
Krannhals and Frantzel observed scarlatiniform eruptions, urticaria, erythema nodosum, and herpes zoster to arise even eight to fourteen days after the termination of influenza. The toxic origin of this late rash presents no difficulty of explanation, since we know that with the antidiphtheria serum the eruption often does not appear until eight to ten days after the injection. A similar explanation holds good for the late appearance of nephritis.
It was the frequency of these eruptions which gave rise to the erroneous supposition at the beginning of the pandemic of 1889 that the disease was dengue fever; for in the latter the eruption is a pathognomonic sign.
In the following paragraphs we will mention a few of the rashes observed in influenza, but without laying claim to an exhaustive description.
Herpes was frequently seen on the usual sites (lips and nose). Teissier terms it, "extremement frequent." Schulz and Demuth found it in 25 per cent, of the cases; Krehl, in 12 per cent.; Bristowe and Petersen, each in 10 per cent.; Stintzing, in 8 per cent.; Anton, in 6 per cent.; and Preston, in 5 per cent.
We found herpes only in 4 per cent, of the cases, namely, out of 105 cases complicated with pneumonia, in 5 per cent,; out of 334 uncomplicated cases, in 3 per cent. Herpes undoubtedly occurs less often in influenza pneumonia, and particularly in the croupous variety, than in the genuine croupous pneumonia.
Teissier describes herpes of the tongue. Herpes zoster of the chest or other portions of the body is frequently mentioned (Real, Dodler, Kollmann, Bilhaut), and particularly as a sequel of influenza following on intercostal neuralgia. (Compare p. 639.) Herpes iris and circin natus were frequently observed (Schwimmer). Of the erythemata, besides the ordinary forms already mentioned, measly and scarlatiniform eruptions, together with urticaria and roseola, were seen (Teissier, Curschmann) in 1.2 per cent, of cases; further, erythema papulatum (Hawkins, Bela Medvei, Moore, Bristowe), erythema nodosum, and erythema multiforme, with or without affection of the joints (R. Guiteras, Schwimmer).
Mention of facial erysipelas complicating influenza is found fairly often, even in the accounts of the older epidemics (1775 and 1847-1848 in England). It has often been noted together with parotitis. No doubt it is due to a secondary infection with streptococci. In the last epidemics this complication is recorded by Laborde, Heller, Heifer, W. Ben net, Lemoine, Mason, Mayor, Schmid, Camenzind, Schmidlin.
Simple and hemorrhagic pemphigus is mentioned several times in the Swiss reports as sequela? of influenza. Purpura hemorrhagica was also of frequent occurrence (Landgraf, Pribram, Locke, Drasche, Ewald, Senator, German army report, Swiss report). Pick (Prague) and Fleury (Switzerland) each describe a case of fatal purpura with general hemorrhagic diathesis.
It is hardly surprising that in a disease accompanied by such profuse sweating as influenza extensive miliary eruptions (cristilina rubra) are not rare.
Purulent forms of dermatitis (folliculitis suppurativa, impetigo, multiple furunculosis, ecthyma) have been frequently observed as sequela? of influenza. Leloir considers that his "Pyodermites acneiques et seborrheiques influenciques " may be the result of infection in two ways: either by direct inoculation of the infectious nasal secretion upon excoriated skin areas, or, endogenously, by the elimination of the microbes in the blood through the glands of the skin. The erythematous forms are most simply classified among the toxic eruptions.
Among rarities and curiosities belonging to the trophic disturbances of the skin we may mention cases reported by Rosenstein (Leiden) and by Sympson, of vitiligo (leucopathia acquisita). Further, "acute gray ness of the hair of the head within a few days" (Bossers in Leyden), premature grayness of the eyelashes (Bock), and finally a case of alopecia areata following influenza (Williamson).
The statistics concerning the frequency of the exanthemata in influenza will vary much according to whether herpes is included or the general vasomotor redness of the skin is designated as erythema.
We found a "finely punctate eruption" altogether in 9 per cent, of cases; in the face alone, in 6 per cent. Exanthemata in the more restricted sense of the term were found by Hawkins in 1 per cent,; Guttmann, in 3 per cent.;Comby, in 6 per cent.; Barthelemy, in 7 per cent, of the cases. Bristowe observed erythematous rashes in 6 per cent, of the cases, a papular or scarlatiniform rash in 20 per cent., while Preston found a papular rash in 2.3 per cent, of the cases.