To the Editor: “Out of the blue”, I received a personal message from a retired nursing sister of a children’s hospital, who had earlier written to the MJA1 describing “a cluster of neonates [who had] simultaneously turned blue” in the 1950s. Her letter to me followed one of mine in the Journal, describing methaemoglobinaemia (MetHgb) in infantile keto-acidosis, where the cyanosis responded rapidly to diabetic control alone.2 Rare as MetHgb is, it has previously been recognised as a presentation of infantile acidosis.3

The cause of the colour change in the neonate cluster “was traced to dye from the hospital’s brandmarks on a batch of new cotton nappies (which had been washed before being marked)”.1 The dye was understood to have been “absorbed into the infants’ circulation via their raw umbilical areas”.

As it turns out, nappy dyes have been incriminated in MetHgb.4 The POISINDEX® System (Thomson Micromedex, Denver, Colo, USA) revealed that the aniline group is among the compounds capable of causing MetHgb through any portal of entry, even intact skin (Stephen Gibbins, Poisons Information Specialist, Victorian Poisons Information Centre, Melbourne, personal communication). Another textile ink, aminophenol, may also lead to the disorder.5 Other common causes of MetHgb are given in the Box.

Aniline dyes were discovered in the 19th century and found useful for inks and for dyeing leather, which they penetrate as they do living skin. They were also used in wood stains, textiles, and oriental rug-making. Because aniline dyes are not indelible and are toxic, they are being superseded by chrome dyes.

The hospital linen room concerned1 reports that they now apply dry, colour-fast pigments using heat-pressed or stamped “transfers” (Administrative Officer, Metropolitan Linen Services, Brisbane, personal communication).

It is not possible to confirm what the “Baby blues”1 dye was — aniline or other. Nor can we now establish whether the dusky colour of the babes was due to absorbed dye circulating passively. Circumstantially however, MetHgb would seem to have been a likely possibility.4

In differential diagnosis, when cyanotic infants or adults without cardiorespiratory signs are encountered, we should not forget MetHgb, drugs and chemical toxins. In patients with MetHgb, the blood will be “chocolate-brown”; and yes — do remember to take a sniff for that exhaled acetone.2