Preschool children (aged 1-5 years) account for 75% of all UK childhood wheezing hospitalisations. This has not changed over 20 years, meaning current treatments are not working and a new approach is needed. Currently, all preschool wheezers are treated with inhaled steroids. However, only about 25% of patients, with allergies, respond well to inhaled steroids; for the other 75%, they are ineffective. This research group has found that some preschool wheezers may have other causes but there are no specific, non-invasive tests to match the right treatment to each child. The goal of this observational study is to test various bedside tests for this purpose in preschool children with wheeze, to see if they are feasible, accurate and acceptable in this age group. The research team would like to investigate the following aims: Aim 1 - To test the proposed panel of simple bedside tests below, to see how accurately they corelate with lower airway infection or inflammation. Aim 2 - To test the acceptability of these bedside tests are to parents and children, and if they reflect the child's symptoms, symptoms control and medication use. Aim 3- A small proof-of -concept study, to test if these simple bedside tests, can be used to determine treatment for each individual child. The panel of simple non-invasive tests that the research team are proposing are: 1. Skin prick tests to common allergies (house dust mite, cat, dog, grass, tree pollen, mixed moulds) 2. Finger prick blood test 3. Phlegm test for bacteria 4. Nose and throat swab for bacteria 5. Lung function test called forced oscillation technique (FOT)