Can a daily powder boost baby gut bacteria and prevent future allergies?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Evidence of personally signed and dated informed consent document indicating that the caregiver(s) have been informed of all pertinent aspects of the study 2. Caregiver(s) meet the following criteria: 1. 18 Years or Older 2. Legal Guardian of the Infant 3. Intending to cohabitate with the infant/toddler for the duration of the study 4. Can be reached by phone and email for the duration of the study 5. Reads, writes, and speaks English 6. Be able to accurately answer all portions of the questionnaire 7. Have access to a working freezer 8. Intending to be primary caregiver and study responder for duration of study 9. Willing to provide synbiotic either in a bottle or some other format to the infant if on a fully liquid diet 3. The PI considers the Caregiver likely to adequately comply with the study protocol requirements based on demonstrated compliance with initial questionnaires and agreement to complete all diaries 4. The infant or toddler enrolled is: 1. Healthy (has not been diagnosed with any chronic health conditions by a pediatrician) 2. Still using diapers (to facilitate sample collection), and expected to continue in diapers for the duration of the study Exclusion Criteria: 1. Infants/toddlers who have a medical condition or history that could increase the risk associated with study participation or interfere with the interpretation of study results, including: * Evidence of major congenital malformations (e.g., cleft palate, extremity malformation) * Any history or suspicion of systemic or congenital infections (e.g., human immunodeficiency virus, cytomegalovirus, syphilis) * Severe gastroesophageal reflux (throwing up or spitting up more than a teaspoon of milk \> 8 times daily) * Chronic vomiting (projectile, bilious or bloody emesis) * Other severe medical or laboratory abnormality (acute or chronic) which, in the judgment of the investigator, would make the toddler inappropriate for entry into the study 2. Infants/toddlers who are presently receiving or have received within three months prior to enrollment the following: * Probiotic supplements * Antibiotics * Medication(s) or supplement(s) which are known or suspected to affect the following: i. fat digestion, absorption, and/or metabolism (e.g., pancreatic enzymes) ii. stool characteristics (e.g., glycerin suppositories, bismuth-containing medications, docusate, Maltsupex, or lactulose) iii. growth (e.g. insulin or growth hormone) iv. gastric acid secretion v. microbiome 3. Infants/toddlers with HIV or hepatitis or lactose sensitivity 4. Infants/toddlers exposed to or displaying symptoms of a disease within 1 month of enrollment, including: * Exposure to COVID-19 * Hematochezia (blood in the stools) * Diarrhea (watery stools that takes the shape of a container \> 5x daily) * Fever (38.2 degrees) * Any other symptom which, in the judgment of the investigator, would make the infant inappropriate for entry into the study 5. Currently participating or having participated in another clinical trial since birth