blaming Archives - usatoday24

We have been blaming hygiene for our allergies for almost 40 years. Ancestral DNA has just shown that the problem is more complex

April 29, 2026 by usatoday24

Every time a child develops a asthmarhinitis or eczema, one of the questions we ask ourselves is why it happens, and one of the ‘culprits’ we point to is excess cleaning. Right now it is a reality that we live in environments that are too neat, using disinfectant gel all the time and not letting the little ones play in the mud because logically they can get stained. However, science here has ‘traveled’ to the past to find out the origin of allergies. What have they done? Here two new and massive studies based on the analysis of prehistoric DNA are putting the famous “hygiene hypothesis“And the paradigm we face now is that the evolutionary adaptations that our immune system has developed over the last 10,000 years to survive pandemics, curiously, are designed to protect you from allergies, not to cause them. A return to the past. To understand the plot twist, we must go back to 1989 where epidemiologist David Strachan proposed the hygiene hypothesis. Here it was proposed that the lack of exposure to microbes during childhood in most modern societies deregulated the immune system, since it literally did not grow with good training under its belt. In this way, it was proposed that, by not having real pathogens to fight against, the body created an imbalance that caused the immune system itself to attack substances that are not actually a threat, such as pollen or mites. And it seemed to make sense. A genetic journey. The first blow to this hypothesis has been dealt by a great published research in Nature this same month of April. Here the researchers analyzed almost 16,000 ancient genomes from individuals who lived thousands of years ago. What they discovered here is that the transition to agriculture in the Neolithic changed everything, since human societies became dense, we began to coexist closely with animals and, with this, large-scale infectious diseases arrived. But these pathogens that we began to face, despite the many deaths they generated, also favored hundreds of immune variants to ensure our own survival. But there is more. This is where parallel research that is revolutionizing our understanding of asthma and autoimmunity comes into play. Here is an article preprint has crossed ancient DNA with the modern complete genome with the aim of looking for differences between our DNA and that of our ancestors. Logic dictated that a system “revolutionized” by evolution to fight bacterial and viral infections of the past would be the cause of today’s allergies. But the data show exactly the opposite, as the study reveals that genetic variants that were positively selected in recent millennia have strengthened defenses in “barrier tissues” such as the intestine, against pathogens, but at the same time reduce allergic inflammation. The variants. Among these defense genes We have, for example, LYZ, which codes for lysozine, a fundamental antimicrobial enzyme in our secretions that destroys part of the bacteria. We also have FUT6, which is involved in protein fucosylation, a process vital to the interaction between our mucosal immune system and the gut microbiome. Why are we allergic, then? If our genetics have been evolving for 10,000 years to protect us from allergies in the lungs and intestines, the question is inevitable: why do cases continue to increase? Here science suggests that the problem is not simply an excess of cleaning in the present, but a profound imbalance. In this way, we do not need to catch diseases or live surrounded by human society, but the problem is that our immune system, genetically adapted to the strong pathogenic pressures of the first agricultural societies, expects to encounter a series of commensal microbes in the environment. The ‘problem’ is that these microbes are no longer present in modern cities and that is why the genes we have with a protective function cannot do their job correctly. Images | Drazen Zigic on Freepik In Xataka | The allergy season in Spain has been extended by 25 days since the 90s. And 2026 brings very bad news about it

We have spent our entire lives blaming spring for our tiredness. Science has just shown that we have lived deceived

March 25, 2026 by usatoday24

March is coming, the days are getting longer, temperatures rise and suddenly our body begins to fill with a feeling tiredapathy and drowsiness that takes over us. Traditionally, this is considered ‘spring astheniaand people, logically, do not stop searching for their symptoms on the Internet and buying expensive vitamin complexes to compensate for the bad feeling that the change of season leaves. But… What is true in all this? A paradigm shift. Until recently, evidence on this phenomenon was scarce and contradictory; however, a key investigation published in the Journal of Sleep Research has recently come to shed light on the matter. The research, led by Dr. Christine Blume from the Center for Chronobiology at the Psychiatric University Hospital of Basel, followed 418 adults from Germany, Switzerland and Austria for more than a year, from April 2024 to September 2025. Every six weeks, participants answered questionnaires about fatigue, drowsiness, insomnia and sleep quality, and at the end of the research they only had to cross-check information to determine if there really was any interfering pattern. with our health. The results. Here what was seen is that a resounding 47% of the participants claimed to suffer from “spring asthenia”, but the reality is that when the information was cross-checked there was absolutely no seasonal or monthly variation in the levels of fatigue, daytime sleepiness or quality of sleep. And statistically the tiredness that people feel in spring is statistically identical to what they feel in autumn or winter. In fact, fatigue in daily activities tended to decrease slightly as the days had more daylight hours, without any specific “peak” of fatigue being recorded during the spring. In this way, the conclusion drawn is that the discrepancy between what people think they feel and what objective data shows suggests that we are dealing with a cultural phenomenon and not a genuine seasonal syndrome. Why do we believe it? This is where the study gets genuinely interesting, since the authors do not simply deny the phenomenon, but rather propose a psychological explanation for why we experience it so convincingly. Nocebo effect: if we expect to be tired in spring, we interpret any sign of fatigue as confirmation of what we thought was going to happen. Cognitive dissonance: good weather generates high social pressure to enjoy it with outdoor activities. The problem is that when the energy does not appear, saying that you have ‘spring asthenia’ is a good excuse to not feel guilty for not following the group. Labeling effect: Like wine tasting better when we’re told it’s expensive, knowing that “you get tired in spring” actively changes how we interpret our own physical sensations. What chronobiology says. It is a reality that we are not robots and that our body reacts to the environment, and this is where chronobiology confirms that there are seasonal variations in sleep linked to the number of hours of daylight we enjoy. Studies in pre-industrial populations in Tanzania, Namibia or Bolivia show that in winter they sleep approximately one hour more than in summer. Likewise, recent research on university students in Seattle confirms that exposure to daylight is vital for our circadian rhythm, however, none of these physiological changes translate into a “clinical picture” or a peak in fatigue in spring. In medicine. Nowadays, when you go to your primary care doctor, it is impossible to receive treatment for ‘spring asthenia’ because it is not included in any official classification. However, doctors warn that a patient who arrives with great fatigue for consultation should not be sent away, even though he relates it to the arrival of spring. It must be remembered that there are many diseases that can cause this condition, such as anemia, a severe allergy, an infection or even thyroid disorders, among others. A lucrative business. While science dismisses the existence of ‘spring asthenia’, the reality is that people’s sensation is the perfect breeding ground for private clinics and dietary supplement brands. When we feel bad, we want a quick solution with a pill, and this makes the sale of multivitamin complexes, caffeine pills and a host of products related to reducing fatigue increase their sales. Images | Vitaly Gariev Arno Smit In Xataka | Only one in four Spaniards has rested on vacation. The culprits: work anxiety and the inability to disconnect

We have been blaming mobile phones for myopia for years. Now we have a much more subtle suspect: lack of light

February 23, 2026 by usatoday24

It is quite a grandmother’s and mother’s phrase to hear that spending a long time in front of a screen or being very close to a book can cause us to develop a disease in the eyes like the myopia. However, science has long suspected that “close work” alone does not explain why myopia has become a global pandemic. The new. Now a revealing study has proposed a physiological mechanism that fits all the pieces of the puzzle together, placing the blame not only on what we look at, but on the amount of light that reaches the back of our eye while we do so. And the investigation is quite justified, since the data is scary. In Spain, 19% of children between 5 and 7 years old are already myopicand projections estimate that by 2050 half of the world’s population will need glasses. To stop this, we need to understand exactly the mechanism that produces myopia, and a team from New York has found the key. The famine of light. The work, recently published in the prestigious magazine Cell Reports by researchers, points to a fascinating concept in this case: the light deprivation hypothesis. Until now we knew that focusing on nearby objects is closely linked to the development of myopia. But what this study has measured with empirical precision is how the myopic eye reacts to the healthy eye during this process. What they have seen. The main finding is that myopes suffer from excessive accommodative pupillary constrictionthat is, when you look closely, the pupil becomes much smaller than normal. If we add to this that close-up work is usually done indoors where lighting rarely exceeds 500 lux, compared to 10,000 lux outdoors, the result is a lethal cocktail for the eye: the combination of dim light and a maximally contracted pupil causes the retina to “starve” due to lack of light. The short circuit. Here the question that logically must be asked is: Why does this lack of light cause the eye to grow abnormally, causing myopia? This is where the purest neuroscience comes in, since our retina processes the image through two main channels: the ON path that is activated with increases in light, and the OFF path, which reacts to shadows. In previous work from 2024, this same team had already shown that in myopic patients the ON pathways have serious deficits, since they are less sensitive and slower. Now the new hypothesis postulates a vicious circle in which, when reading or looking at a cell phone indoors, the pupil closes too much. And this is a problem, since chronic lack of light further weakens the retinal ON pathway, and this imbalance sends erroneous signals that ultimately promote elongation of the eyeball. The treatments. This proposal not only stands out for explaining the biological mechanism of myopia, but also unifies at once why the treatments that ophthalmologists They have been applying it empirically for years. One of the examples is spending time outdoors, but not because it cures, but because the sunlight is so intense that it more than compensates for having a small pupil, keeping the ON pathway stimulated and slowing the progression of myopia. Another example is the use of atropine drops in children to stop myopia thanks to the dilation of the pupil so that more light enters the retina. The same goes for multifocal lenses that are used to reduce accommodation effort, since the pupil does not need to constrict as excessively. It is not definitive. As is almost always the case in science, this work does not demonstrate a direct coincidence yet, but rather offers us an incredibly solid and plausible physiological mechanism supported by very robust data on the behavior of our pupil and neural pathways. But there is still a way to go with new long-term studies to confirm the hypothesis 100%. While we wait for those results, the practical conclusion seems clearer than ever: the problem is not just the tablet or the book. The problem is doing it in the dark, so if you are going to strain your eyes up close, make sure you turn on a good lamp and, above all, don’t forget to go out into the sun. Images | Akshit Dhasmana In Xataka | Denialism has reached one of the last corners of science still free of it: seeing glasses

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