Why do fingernails grow faster in the summer?

[AidanHarding]

Anyone know?

[DrFidelius]

Do they?

[Qadgop_the_Mercotan]

No, I don’t believe they do.

@Dan Mitchell

William B. Bean studied his own nail growth for 35 years and published the data in Arch Intern Med, 1974, Vol. 134, 497-502 (30 yrs) and ibid, 1980, Vol. 140, p. 73-76 (35 yrs). He found that nails grow more slowly
with age; growth rate at age 32 was 0.123mm/day, but by age 67 had decreased
to0.095mm/day. No variation with geographical location, physical activity,
or season.

Got any reputable sources that say they do grow more in summer?

QtM, MD

[Moirai]

I don’t know about summer, but I think they can grow faster and stronger depending on the vitamins you are taking. When I was pregnant and taking huge vitamins, my hair and nails seemed to grow in faster, stronger and thicker. Maybe it was the hormones, though.

[kniz]

I believe they grow faster in the summer but have nothing to prove they do. However, I do not believe that stuff about growing slower the older you get. I noticed mine need cutting this evening. It seems like I just cut them and it’s been like that more and more. I guess maybe that’s what they mean by YMMV.

[AidanHarding]

I asked because mine seem to and Googling has produced plenty of sites with “facts” about nails claiming that they do grow faster in the summer, but no explanation as to why.

I don’t really have what I would consider an authoratative source to say that they definitely do grow faster in the summer, let alone one to say why.

Oddly enough, the reason I keep them very short is from playing water polo at school where referees at competitions would check your nails to make sure that they were short and you couldn’t harm the opposition with them.

[PetW]

is water polo only during summer?

[AidanHarding]

No! We used to play all year round at school, but I stopped playing before my exams and never started again, so I don’t know if there is a “season” at senior level.

[KidCharlemagne]

Virtually every source I can find says that nails grow faster in the summer although few offer a reason. Even adding “myth” to a google search doesn’t turn up any sources that contradict that notion. Of course, scientists aren’t immune to myth either but:

http://www.aad.org/pamphlets/nailhealth.html

Nails, like hair, grow from the matrix. As older cells grow out, they are replaced by newer ones, they are compacted and take on a hardened form. The average growth rate for nails is 0.1 mm each day; individual rates depend on age, time of year, activity level, and heredity. Fingernails grow faster than toenails. Nails also grow more rapidly in the summer than in the winter. Nails on a person’s dominant hand (right vs. left) grow faster, and men’s nails grow more quickly than women’s, except possibly during pregnancy and old age. Nail growth is affected by disease, hormone imbalance, and the aging process.

This guy offers a believeable reason:

http://www.newton.dep.anl.gov/askasci/gen99/gen99671.htm

His reasoning is an increase in metabolism in many people during the summer and
a difference in diet, though the former sounds like it would have a greater effect. As far as Qadgop’s source, it wouldn’t surprise me if a guy who measured his nail growth for 35 years didn’t get out much, even during the summer.

[KarlGauss]

Here is another cite that shows that even among healthy young men, there were no seasonal peaks in nail growth (see the last line of the abstract).

I speculate that people think their nails grow faster in the summer since they tend to get dirtier in the summer, i.e. gardening, outdoor sports, and other summer activities all tend to promote the deposition of dirt under the nails and that draws attention to their length.

[KarlGauss]

In addition to the references that Qad and I found (above) which state that there is no seasonal or summer effect on nail growth, this rather erudite article also makes no mention of the phenomenon (see section entitled ‘Nail growth’).

Sounds like this “fact” has taken on a life of its own.

[KidCharlemagne]

@KarlGauss

In addition to the references that Qad and I found (above) which state that there is no seasonal or summer effect on nail growth, this rather erudite article also makes no mention of the phenomenon (see section entitled ‘Nail growth’).
Sounds like this “fact” has taken on a life of its own.

How do you get that from this?

The nail plate is approximately 0.5 mm thick in females and 0.6 mm thick in males, and it tends to increase with age. The nail grows at a rate of approximately 1.8-4.5 mm per month (Johnson, 1991) or 0.1 mm per day; thus, the average nail can regrow completely in 6-9 months. A number of factors can affect the rate of nail growth (Douglas, 1959; Guy, 1990; Johnson, 1971; Johnson, 1991; LeGros-Clark, 1938; Orentreich, 1979; Seaberg, 1991). Periods of stress or illness can detrimentally inhibit nail growth, while biting or short trimming of the nail can accentuate growth. The hardness of the nail is dependent on the onychocyte bands, matrix proteins, and the hydration level of the nail (Baran, 1974). The water content of fingernails varies from 10-30%. Brittle nail plates have lower water contents.

All I can find is that "a number of factors can affect rate of nail growth. " I don’t think that anyone would say that there is an inherent seasonal cycle to nail growth, but more likely that some of the factors that affect nail growth change from winter to summer in some zones. I don’t see it as very far-fetched, nor do I see it as particularly contentious if you don’t consider the season to be the proximate cause. Perhaps there is a decrease in stress in the average person, which your article does indicate can affect nail growth. Having said all this, “summer” wouldn’t be my first choice of causes to link to nail growth. It’s hardly scientific. It’s not that I believe that summer is even correlated with nail growth, but there hasn’t been much evidence either way.