“Decreased Diabetes type 2 risk at high intake of high- but not of low-fat dairy products suggests that dairy fat partly could have contributed to previously observed protective associations between dairy intake and diabetes type 2”
Read the full study here: https://pubmed.ncbi.nlm.nih.gov/25832335/
And keep in mind that what shows up as the most allergenic compounds when we doo food allergy testing are casein and lactose - both very low in butter and cream, hence the reason small amounts of these full-fat items carry health benefits to them, especially as they contain butyric acid which is key for healthy gut flora.