Summary
Dermatological therapy in the first few weeks of life must take into account the desire that the parents have for a baby with “perfect skin” and the special care that is required due to the therapeutic risks specific to the neonate’s skin.
1 - SPECIFIC FEATURES OF THE NEONATE’S SKIN
1.1 - THE NEONATE AT TERM
The skin of a neonate at term is no different to a child’s skin in terms of its architecture and thickness. Its does not differ notably from older children’s skin in terms of permeability but the ratio of surface area to weight is much greater in a term neonate. Furthermore, the presence of an occlusive nappy can in itself cause systemic toxicity when local treatments are used in this area.
The vernix caseosa, which is made up of proteins, lipids, water, foetal corneocytes and a hydrophobic lipid matrix, covers the skin of the foetus during the third trimester of pregnancy. It is known to have a role in hydration and preventing infection, and it also encourages the development of the “cutaneous acid mantle” and facilitates physiological colonisation of the skin. It is therefore sensible to leave it in place but this is contrary to what is currently practised in maternity units.
Transient cutaneous vasomotor or perspiration abnormalities do not have any particular impact on treatment options for the skin. However, neonates do have relatively dry skin and this must be taken into account when choosing topical treatments.
1.2 - PREMATURE NEONATES
Prior to 32 weeks gestational age, the premature baby’s skin is characterised by a greater permeability and fragility and these are additional factors for morbidity and mortality in premature infants. This cutaneous permeability gradually decreases after birth until it becomes identical to that of a term baby; the time taken for cutaneous maturation is around two weeks. This time period is shorter in black neonates and female neonates, while it is longer in extremely premature babies (under 26 weeks gestation). This greater skin permeability should therefore be taken into account when choosing topical skin treatments for use in premature neonates and this, as well as other factors related to immaturity, may increase the risk of toxicity.
2 - THE RISK OF PERCUTANEOUS TOXICITY IN NEONATES
Neonates are at risk of percutaneous toxicity because:
- The ratio of skin surface area to weight is three times greater in term neonates and six times greater in premature babies born before 32 weeks than the ratio seen in children;
- The area that is covered with a nappy accounts for between 10 and 20 % of body surface area and this kind of occlusion increases the transcutaneous passage of the topical treatments applied in this region;
- The organs involved in neutralising and eliminating potentially toxic substances are physiologically immature, especially in premature babies. This may be the case for the liver (the oxidation and glucuronidation systems), the kidneys (physiologically low glomerular filtration in neonates) or the blood (hypoalbuminaemia).
Of course, the presence of cutaneous disease involving deterioration to the stratum corneum (congenital ichthyosis, epidermolysis bullosa) is a further risk factor for percutaneous toxicity. The list of medications and substances that are potentially dangerous for neonates is not limited to the products mentioned in Table I. The progression of management techniques and the increasingly earlier term at which infants are cared for may lead to cutaneous presentations that have not to date been encountered.
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Therapeutics in Dermatology, Fondation René Touraine © 2001-2012