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24 votes
Accepted

Can UV radiation be safe for the skin?

You're talking about long-wave UV, or UV-A radiation. In the 80s, experts claimed that this was a safe wavelength. Protection against UV-A was not part of sunscreen in the early days. Consequently, UV-...
S Pr's user avatar
  • 6,222
17 votes

Why does UV radiation from the Sun cause skin cancer?

Rather than 'breaks' caused by high energy radiation, UV radiation causes chemical modifications of the bases ('letters') that make up DNA. There are four bases in the DNA alphabet abbreviated to A,T,...
mimat's user avatar
  • 1,425
15 votes

Why does UV radiation from the Sun cause skin cancer?

There are very many photochemical reactions: Up to 50–100 mutagenic reactions on DNA per second might occur in a skin cell during exposure to sunlight, but are usually corrected within seconds by ...
bandybabboon's user avatar
  • 10.4k
10 votes

Why hand washing causes skin to dry?

I will assume the hand washing you speak of involves soap. The human skin (which also covers hands) is a complex organ with an underlying system of glands. One of these is the exocrine sebaceous ...
Chimango Chisuwo's user avatar
10 votes

Why are bald heads so "shiny"?

Think of what happens when you don't wash your hair for days. It gets oily and greasy. This oil-like substance on your hair is called sebum and mainly works as a lubricant . The Sebaceous glands ...
Eleftheria Chatziargyriou's user avatar
9 votes
Accepted

Why are skin moles (pigmented spots) circular in shape?

Note: I am not stating that moles are in general circular in shape because there are no statistical studies to conclusively state so. This answer is mostly about default circular shape of cell ...
WYSIWYG's user avatar
  • 35.6k
9 votes

How lethal is high dose UV?

The answer is easier than you think. Have you ever had a sunburn so bad that it causes blisters? (I have, as a teen falling asleep on the beach.) Those sunburns are called second degree sunburns. With ...
anongoodnurse's user avatar
8 votes
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Why the smell of sweat greatly varies across the body?

Sweat is actually odorless regardless of what type of sweat gland it comes from, of which there are two types - apocrine and eccrine. As suggested by canadianer, the odor comes from the mixture of ...
PreMedHopeful's user avatar
8 votes
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Why did evolution make people's skin dark?

It didn't, the basal condition for humans is dark skin, all other pigmentation patterns evolved from it. Additionally Dark skin is not monophyletic/homologous in humans, that is some darks skinned ...
John's user avatar
  • 14.7k
7 votes

Can UV radiation be safe for the skin?

There are (at least) two sides to this story. One is direct DNA damage being caused by UV-B light which happens to have photons with just the right amount of energy to interact with thymine. This has ...
Damon's user avatar
  • 259
6 votes
Accepted

If cells regularly renew, why do we have scars?

Scar tissue formation is part of the normal healing process in which fibrous material braces and pulls the wound together, in other organisms (and young mammals) this process is mild and just serves ...
John's user avatar
  • 14.7k
6 votes

Why does hair turn white but not skin?

The answer to this question has its reason in the hair cycle. Our hair goes through a cycle of growth. At the end of this cycle, the cells in the hair follicle die and have to be replenished before a ...
Chris's user avatar
  • 51.6k
5 votes

Why sun rays don't burn our skin?

Proteins and DNA absorb light in the UV spectrum (both UVA and UVB) because that is the energy level at which pi electrons in the aromatic rings get excited (nucleotides and aromatic amino acids have ...
alec_djinn's user avatar
  • 3,108
5 votes

Why sun rays don't burn our skin?

The reason that UV light causes sunburn, while normal light does not, is not founded in the energy carried by single photon. As stated on wikipedia: Importantly, both sunburn and the increase in ...
Nicolai's user avatar
  • 4,391
5 votes
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How is sebum secretion regulated?

Nice question! Unfortunately, the complete list of pathways involved in regulation of sebum production and secretion rate by sebaceous glands are not understood yet (Picardo et al, 2009). However, we ...
another 'Homo sapien''s user avatar
5 votes
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Can viruses pass through sweat pores?

'Pore' is a confusing term. Sweat is produced in sweat glands, and subsequently excreted through a duct, as indicated in the image below (sudoriferous ~). In short, viruses cannot enter the body ...
MBever's user avatar
  • 168
5 votes

Do goosebumps always appear in the same spots on the skin?

Goosebumps are caused by the contraction of the arrector pili muscles, which are attached to hair follicles. Accordingly, they appear at the same spots on one's body every time.
SplitInfinity's user avatar
5 votes
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How and why do skin tags develop?

Given that skin tags are considered benign, it doesn't surprise me to find very little published research focusing on them. It's unlikely that much grant money exists to answer questions about them. ...
Forest's user avatar
  • 1,879
5 votes
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Can pathogens enter the bloodstream if the epidermis has been scraped off?

Our epidermis is the first line defence against natural infections; it is also a part of the innate immune system. This is due to it contains a layer of dead cells that separates the living cells of ...
Arnb's user avatar
  • 511
5 votes
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Why does UVA penetrate deeper than UVB, though it's weaker?

Our skin contains quite a lot of water and I think this is answers the question: The absorption of UV light by this water goes drastically up when you shift to shorter wavelengts with a minimum ...
Chris's user avatar
  • 51.6k
5 votes

Is there any difference between fascia and skin ?Are both the different names of the same thing?

The superficial fascia is the lowermost layer of the skin found in nearly all parts of the body and it usually blends with the reticular region of the dermis. But that doesn't mean it's a part of the ...
Corina Gerontakis's user avatar
4 votes

Why can silicone reduce keloid?

Keloid scars are formed when the scar tissue extends beyond the margin of the original wound and is the most extreme type of scarring. When this scar type occurs, a small wound such as an insect bite ...
Beautymedi's user avatar
4 votes

Do skin mites reproduce on human face during night?

Yes, it is true that these mites exist on healthy human skin, on >98% of people, no matter the country or hygiene. However, I'm sorry to say that this photograph is not the follicle mite Demodex ...
Jared Bernard's user avatar
3 votes
Accepted

Why are all human beings not black in color?

First let's look at the difference between light skin and dark skin: darker skinned people have higher concentrations of melanin than those with lighter skin. Africa is located around the equator, a ...
rjames's user avatar
  • 46
3 votes
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Healing of Skin Superficial Wound

Skin is composed of layers, the uppermost being the epidermis. Upper layers of the epidermis (dry, flat cells tightly packed together, and of varying thickness on different parts of the body) can be ...
anongoodnurse's user avatar
3 votes

Why are skin moles (pigmented spots) circular in shape?

Short answer Naevi do not have to be circular in shape. In fact, they come in a wide variety of shapes and colors. Background A beauty spot, or mole is called a naevus. Naevi (plural) are formed by ...
AliceD's user avatar
  • 52.4k
3 votes

Do "scars" in humans replace all the skin layers or only some layers?

This depends on how deep was the initial wound, and how that wound healed. There are mainly two ways a wound could heal, either by primary intention (like in surgically closed wounds), or by secondary ...
Matt Dee's user avatar
  • 189
3 votes

Function of Smooth Muscles in the skin

Smooth muscle in the skin actually produces very little motion. They are found in special places, such as the areolas of the nipple, the tunica dartos of the scrotum, and also around hair follicles. ...
rotaredom's user avatar
  • 2,711
3 votes
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Why do scabs itch?

Part of this is due to the immune response to such an injury, which causes some amount of inflammation leading to histamine release - the introduction of this paper has a nice overview. In addition, ...
Jared Andrews's user avatar
3 votes
Accepted

Which kind of drugs get absorbed through epidermis?

According to a review (Prausnitz2004), marketed drugs with a dermal route of administration tend to fulfil the following criteria : Small molecular size (< 500 Da) High lipophilicity Small ...
Eliane B.'s user avatar
  • 1,145

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