I have some used baby clothes that looked clean when I packed them away, but when I got them out to prepare them for the birth of my second child, they had yellow stains around the neck from spit-up and/or formula. Can anything get these stains out?
This happens a lot as we think things are clean but storage seems to find those not so clean areas. Not uncommon to see this in stored underwear, sheets, and towels. The yellowing results from oxidation (slow reaction with oxygen in air to change color) of unremoved stains usually has a protein component that needs to be removed. These are big, complex structures that are best broken down using enzymes. Unfortunately, these materials are not found in every laundry product and they are rather slow to work.
What I would suggest is find a good powdered detergent like Tide, not Tide with Bleach. The trick is to make sure the detergent is dissolved before adding the clothes. Make a COOL water presoak solution either in a bucket or use your washer set for lowest water setting. (Trick #1 — add detergent with hot water first, swirl to dissolve, then switch to cool/cold water) Add the recommended dosage for best results. Let the old baby items sit in the presoak for a long time (minimum 8 hours or even overnight). Trick #2 — occasionally swirl or agitate the presoak solution to help encourage better penetration of the soils and removal of the top layers. Finally, wash in the hottest water recommended on the care labels. The warmer the water, the better the removal. If items are bleachable, consider using 1/2 to 3/4 cup Clorox Regular-Bleach. Do the quick Bleachability Test if uncertain (2 tspn liquid bleach in 1/4 cup water; apply a drop on a hidden area like inside seam, hemline or cuff; wait 1 minute and then blot with towel); no color change means it is safe to use bleach on the item.
Don’t forget to check for success after washing and before drying. You might need to retreat the item.