There have been reports of certain lash serums containing an ingredient called prostaglandin analogs (such as bimatoprost or isopropyl cloprostenate) that can potentially cause fat loss in the area where the serum is applied. These ingredients are commonly used in prescription medications for glaucoma and can have the side effect of reducing fat in the treated area.

It's important to note that lash serums containing prostaglandin analogs are typically available as prescription-only products and should only be used under the guidance of a healthcare professional. These serums are not typically found in over-the-counter lash growth products.

If you are concerned about the potential side effects of lash serums or any other skincare product, it is always best to consult with a dermatologist or healthcare professional before using them.