The primary aim of this study is to investigate the relationship between skin barrier structure/function and skin health in a longitudinal birth cohort. The study (including the purpose and design) has been externally reviewed by a group of peers and was awarded funding by the Leo Foundation.

There is no therapeutic intervention and we will offer no healthcare advice. All participants will be instructed to seek medical care as needed from their normal service provider. As such there are no significant ethical implications.

This study involves a series of harmless procedures to test the properties of the skin in babies and the collection of information on how parents care for their baby's skin over the first 12 months of life. All types of procedures to test the skin are non-invasive and have been used safely in previous clinical studies in babies. Whilst FTIR spectroscopy was used in a previous study conducted by our team in babies (the OBSeRvE study), the investigators will now use a different FTIR instrument. Compared to the benchtop device used for OBSeRvE, the new instrument is better adapted to remote use because of its portability, is safer to use because the measurement head is made of rugged inert materials (diamond and stainless steel) compared to a fragile loop, and the detector is electrically cooled by batteries instead of liquid nitrogen. This device has been tested in humans for safety.

The approach to recruitment of study participants has been informed by the experience of several other clinical studies in babies, including the Barrier Enhancement Eczema Prevention Trial, for which Sheffield has just recently finished recruiting 250 babies. Study recruitment and the skin procedures performed shortly after birth will be led by an experienced Sheffield Teaching Hospitals Research Midwife who is familiar in this clinical environment, and is comfortable with the ethical implications of working with babies and new mothers in the early stages following birth. The Research Midwife will perform the study duties, while remaining sensitive to the needs of the women and babies on the postnatal ward (for example allowing women to breastfeed in peace if requested), and ensuring throughout that maternity service provision will not be adversely affected. The Research Midwife is fully trained in good clinical practice and informed consent. Babies will only be included in the study if the mother's consent is freely provided. Every effort will be made to minimise the burden placed on parents: this means that the researchers will go to the participants to undertake the tests, either at the hospital or at their homes.The researchers will also distribute vouchers to the participants as a "thank you" for their involvement in the study. The voucher amount will be proportionate for their involvement, and is at an appropriate level for the burden of taking part. Taking part is entirely voluntary and the researchers will observe the customs/wishes of the participants. An experienced Research Midwife will lead all hospital assessments, with subsequent follow-up visits being lead by skilled University of Sheffield employed Skin Research Technicians who hold a Sheffield Teaching Hospitals research passport and have undergone a full Disclosure and Barring Services check. All participants will be notified prior to discharge from the maternity ward that the study team conducting home visits consists of both male and female members. If the participant is not happy for a male researcher to conduct a home visit, the researchers will ensure a female member of the team is available as a replacement.

This study includes skin assessments at the participant's home. The research team will complete a lone worker risk assessment and will comply with The University of Sheffield and Sheffield Teaching Hospitals NHS Trust Lone Working guidance. The researchers will issue a study mobile phone for communication during lone working episodes. The researchers have established a set of inclusion and exclusion criteria to ensure that the study is conducted fairly. To ensure that the results are generalizable the researchers have kept the exclusion criteria to a minimum with a geographical restriction centred on the Jessops Wing Maternity Unit established simply for logistical reasons (follow-up sessions being conducted at the participant's homes). The participants will be advised that their data will be held securely, identified only by a unique study number, and that all personal information will be kept strictly confidential. Identifying personal details will be kept only on the study registration form and the Consent form. These documents provide the only link between personal information and the study participant number, and will be kept separately from study data, and stored securely in the STAR study office. Pseudonyms will be used for purposes of transcription and verbatim quotation within any publication. Audio recordings will be destroyed after transcription analysis.