[timsmith (OP)]

When someone cuts my fingernails they feel weak afterwards. Why is this?

[chris]

I remember complaining to my parents when I was small and they cut my fingernails that it made "my fingers feel weak" afterwards, so you are in good company!

I think the reason for this strange sensation is that the fingernails provide rigid support to the ends of the fingers. We rely on this to enable us to feel things and explore things when we touch them with our fingertips.

When the fingernails are cut short we lose some of this support, which can make the finger-ends feel more exposed and more flexible than normal. This might be more pronounced in smaller people because the nails are softer than in an adult, hence you notice the "weak" sensation to a greater extent.

[crystalbrincks]

Maybe not a scientific enough approach, but my friend was told by her nails master that the longer nails grow the thicker they get as our body feels nails should be protecting more and more surface. Though it doesn't always work this way because people can have issues with weak nails no matter they are long or cut

[chris]

Very interesting @crystalbrincks thank you. Although in the case of a young person having their nails cut by a parent, the nails are probably not that long or thick? So is the increase in thickness that appreciable over a short distance and hence able to explain the reported sensation of "weak-feeling" fingers?

[Nika2003]

I think that the Cosmetic industry is trying to convince us that the main reason for the fragility of nails is illiterate nail care, and in particular, a bad manicure. This is true, but this is not the main reason - it is one of many. After all, there are women who rarely do manicure or do not do it at all, and the condition of their nails is completely different: some have their nails even and strong, and someone suffers and suffers from their fragility all the time. In addition, this problem is familiar to many men.
The use of aggressive household chemicals is also often put on the first place, however we do not erase, do not clean the dishes or shells with our feet, but the toenails are also often subjected to negative changes, and become as fragile as on the hands. This is no less dangerous, and even more: if the hands are always in sight, we keep our feet in closed shoes for most of the year, and here an inattentive attitude can lead to fungal infections that turn into serious diseases. Nails on their legs can be destroyed and even completely peeled off from their fingers - that is, they can simply be lost.
About fingernails or nails on arms or hand it is spoken more often and more, therefore at first we will tell about problems of fragility of fingernails or nails on legs or foots. In most cases, the problem is due to weak immunity associated with other factors: exposure to radiation and electromagnetic radiation, the intake of various drugs and heredity. The latter factor is not so common, but its influence must be taken into account. These are the diseases that are now active: these are problems with thyroid, liver, adrenal glands; diabetes, psoriasis.
Sweating and tight shoes are also frequent causes of problems with the nails.
I think I helped you with the information.