The Cow's Milk-related Symptom Score (CoMiSS) tool has been developed to define a score to recognize cow's milk related symptoms in infants and young children.

Many infants and toddlers with symptoms that can be related to intake of cow's milk and cow's milk protein allergy (CMPA) are often not diagnosed due to the lack of specific markers.

The goal of this trial is to validate the CoMiSS tool in infants suspected of CMPA and investigate if the CoMiSS tool could be an alternative to the open challenge test needed to confirm the diagnosis of Cow Milk Protein Allergy.

Inclusion Criteria:

• Male or female infant aged up to 6 months old
• Has been fed exclusively on cow's milk infant formula for at least one week
• Has CMPA symptoms that have been present for at least one week, and that developed within the first two months of starting cow's milk infant formula
• In the opinion of the investigator, requires a two week elimination diet with Amino Acid Formula (AAF).
• Had a gestational age at birth of 37 to 42 weeks
• Had a birthweight of 2500 g to 4500 g
• Informed consent signed by both parents, liable parent or legal guardian (if applicable).

Exclusion Criteria:

• Has ever received either an extensively hydrolysed infant formula or an AAF prior to enrolment
• Has a fever above 38.5°C at enrolment
• Has ever experienced a medically diagnosed serious anaphylactic reaction
• Use of antibiotic drugs at enrolment. Infants may be enrolled if antibiotics have been stopped at least 7 days prior to enrolment. (Antibiotic treatment can be initiated during the study if an infant develops a condition after enrolment that requires antibiotic treatment).
• Infant with a health condition or family situation that makes the infant unsuitable to participate in the trial according to the opinion of the investigator
• Infant or infant's carers are unable to comply with trial procedures
• Currently participating or has participated in another clinical trial within 4 weeks prior to trial start.