Table 1.

Inclusion and exclusion criteria

Inclusion criteria
Antenatal maternal
1	History of doctor-diagnosed atopy (atopic eczema, asthma or hay fever) in the woman, her partner or other child the couple have parented.
2	Woman aged 18 years or older.
3	Woman able to understand English.
4	Lives in a hard water area (>250 mg/L calcium carbonate).
5	Lives in a property suitable to have a water softener fitted.
6	If in a rented property—agrees to seek consent of landlord for fitting of water softener device.
7	Agrees to have water softener±additional tap for drinking water fitted at home.
8	Agrees to researchers accessing pregnancy and pregnancy outcome data for the mother and child.
9	Able and willing to give informed consent.
Postnatal maternal
10	Maternal consent for her neonate to participate in the study.
Exclusion criteria
11	Preterm birth (defined as birth prior to 37 weeks’ gestation).
12	Significant inflammatory skin disease at birth not including seborrheic dermatitis (‘cradle cap’).
13	Sibling (including twin) previously randomised to this trial. If multiple birth, the first child will be randomised into the trial.
14	Any immunodeficiency disorder or severe genetic skin disorder.
15	Child has any other serious health issue which, at parent or investigator discretion, would make it difficult for the family to take part in the trial.
16	Planned stays away from home for a continuous period of more than 2 weeks or a total of 1 month out of the 6-month follow-up period.
17	Water softening or filtration device already installed.
18	Concurrent enrolment in any other skin-related intervention study.
19	Other medical condition that in the opinion of the chief investigator could interfere with the conduct of the trial.