It might be going too far to say that the face is the mirror of the soul, but there is often an element of truth in these pearls of popular wisdom. Dermatologists often tell us that our skin, the largest organ of the human body and one of the most complex, and our brain are connected in such a way that everything that affects our state of mental wellbeing such as stress or anxiety also has an effect on our epidermis.
So what is the evidence behind this connection? Dr Natalia Jiménez, a dermatologist at Ramón y Cajal Hospital in Madrid and an expert in the cosmetic side of her speciality, explains:
"The two are much more closely related than most people realise. It is evident even in the embryonic stage. All the cells in our body derive from three layers: ectoderm, mesoderm and endoderm. Curiously, the development of the brain and the skin come from the same layer, the ectoderm. In other words, the skin and the brain have the same origin from the earliest stages of a human being," says this expert in her book, Ponte en Tu Piel (which could be translated as "Put Yourself in Your Skin").
In it she gives advice on skincare which is based, first, on knowing enough about our skin, a step we normally skip when we want to improve it. She says that understanding how skin functions will help us to take action and obtain better results for less money.
And one of the keys, before we rush to fill our makeup bags with creams, phials and serums, is to remember that "our skin can reflect our emotions".
"That's why we blush in embarrassing situations or we come up in goose bumps in response to certain situations," Dr Jiménez says.
She explains that the principal enemy for a lovely, healthy skin is stress. "It causes a concentration of cortisol and adrenalin in the blood and that leads to skin problems," she says. And although nervousness is not the only cause of the most common skin problems treated by dermatologists (atopic dermatitis, psoriasis, rosacea, acne), it is a factor that triggers outbreaks.
Dr Jiménez confirms that it is much harder to achieve an improvement in these conditions through medication and creams alone. In most cases some deeper, more fundamental changes are needed to obtain the best results, even though patients are often sceptical when they are told that.
"We tend to trust a cream which promises miracles and is recommended by a friend more than advice from a professional. That is always the way when it comes to skin problems," she says.
Well, just for a change, let us take notice of the experts and try to improve our skin without miracle formulas. What should we do?
"To start with, a bit of exercise and, if possible, some yoga or meditation," Dr Jiménez says.
She has seen that a little physical exercise a day (we don't need to become athletic) improves the condition of the skin. There are studies that show that exercise helps to preserve and renew collagen, which is basic for firmness, and elasticity. And perspiring also helps blood circulation and "cleans" the skin. And another easy piece of advice to follow is to sleep between six and eight hours a night. Some research has shown that sleeping for five hours or less can result in more wrinkles appearing. Also, experts say that during sleep collagen and elastin are produced naturally and the skin is oxygenated and regenerates.
Exercise, sufficient sleep, avoiding toxins like tobacco, alcohol and sugar... "Our skin condition depends 75% on good habits and 25% on genetics," says the doctor. The amount we inherit from our parents is not negligible, but we can ruin our hereditary advantages if we are not careful. "For example, sunbathing without using protection, which is the main cause of ageing skin," Dr Jiménez says.
In fact, of all the routines she recommends in her book to improve different types of skin, factor 50 sun protection (or higher) is the key. We must never forget to use it, she says, and it must be applied all year round. With that and a few inexpensive cosmetics, skin can be healthy and lovely. There is no need to spend a fortune on treatments and creams.
"We see people who use botox in the winter and have marks removed by laser and then in the summer they go and sunbathe without using anything to protect it," she says.
The skincare recommended by Natalia Jiménez, which is followed by celebrities including model and actor Jon Kortajarena, is based on good habits and a few effective products (she is a big fan of retinol as part of the nighttime skin care routine).
"Nobody needs interminable skincare routines, even though they have become fashionable these days," she concludes.
In her book, Natalia Jiménez dispels numerous myths about the skin. For example, that to keep it looking lovely, hydrated and well cared-for we have to drink two litres of water a day.
“Drinking water is good for the general functioning of the body but skin hydration is not down to the amount of water you drink; it depends on the amount of moisturising cream you use,” she says.
For conditions that get worse with stress, it is important to keep the skin hydrated, she insists, otherwise the protective layer does not function as well as it should and the skin can flake and peel.