A citrus drink on vacation is a terrible idea. And it's not about alcohol at all

The dangerous relationship between plants and sunlight is best known in the context of Sosnovsky hogweed. It is a dangerous invasive species that, despite efforts, still cannot be eradicated. Every year, especially in June and July, we hear warnings about the potential for burns from touching this herb in combination with sunlight. Although the most well-known, Sosnovski's hogweed is just one of many photosensitizing species we can find in Poland. Painful burns threaten us after excursions in meadows and fields far more often than is commonly believed.

- The toxicity of Sosnovsky hogweed is determined by the furanocoumarins, or photosensitizing chemical compounds, contained in it, explains Professor Adam Matkowski, head of the Department of Pharmaceutical Biology and Biotechnology at the Wroclaw Medical University. - The plant produces them for defensive purposes, and by themselves they are not very dangerous to humans. The problem begins when an additional factor kicks in: UV-A radiation. Then only the compounds that previously penetrated the skin begin to activate. Therefore, erythema, blisters, pain or swelling of the skin do not appear immediately after contact with the plant, but sometimes even after many hours. Thus, it is possible not to associate the cause with the effect and not to connect the ailment with a nature hike half a day ago.

The inflammation of the skin caused by a combination of plant action and sunlight is called phytophotodermatosis. In Sosnovsky hogweed, especially in the sap contained in the stems and leaves, the concentration of furanocoumarins is high. Hence the high toxicity of this herb, as well as its "cousin", as another species of hogweed originating from the Caucasus region - Mantegazzi's hogweed - can also be found in Poland. In terms of appearance, the differences between the two are insignificant, possible to recognize actually only by specialists. However, as Prof. Adam Matkowski points out, it doesn't matter to the average person. Whether the burns were caused by contact with such or other hogweed.
- the effect is more or less similar, painful and sometimes long-lasting. It is also worth adding that a small amount of radiation is enough to activate furanocoumarins, so it can happen even
on a cloudy day.

Pine hogweed belongs to the celery family and also has other nasty relatives.

- These include, for example, wild parsnip, angelica, and even, albeit slightly, the popular culinary and edible celery - or rather, its leaves, calculates Prof. Matkowski. - While there are fewer photosensitizers in these plants, the effects of contact with the green parts and flowers can also be severe. The yellow flowers of wild parsnip or angelica may seem attractive, but it's better to stay away from them, and don't approach celery harvests without gloves. Also photosensitizing is buckwheat, which comes from another family, or rather its green parts.

Another family whose representatives can harm our skin when exposed to UV radiation are the rutaceae. Among them, the most phototoxic is rue, often grown in gardens for its pretty appearance and pleasant fragrance. Ruta has medicinal properties, being rich in rutin (a flavonol glycoside - added, among other things, to popular antipyretics) but also contains furanocoumarins.

Wildlife lovers can be advised: you don't know the plant - it's best not to touch it. If you like it very much and you absolutely must have it in a bouquet of field flowers - use a wildlife specimen recognition app on your phone. And just to be sure, wash your hands thoroughly after a trip to the outdoors.

Sometimes, however, the enemy can attack from a completely different direction. Sun, beach, lounger, and hands a refreshing drink with citrus - who does not dream of such a vacation? This idyllic vision is brutally brought down to earth by the knowledge of a naturalist:

- Just don't citrus! - warns the head of the Department of Pharmaceutical Biology and Biotechnology and the UMW Botanical Garden of Medicinal Plants. - They too belong to the rutaceae family, and some are also rich in photosensitizers. The highest concentrations are found in the peel and, in addition, they dissolve very well in alcohol. All it takes is a few drops spilled casually on exposed parts of the body, and the sun will do the rest.

The highest concentrations of furanocoumarins are found in limes and grapefruits, but lemons and oranges are also not free of them. Phytodermatosis after sunny drinks has even lived up to its colloquial name: in some countries it is known as "dermatosis margarita."

Another type of photosensitizing compound (hypericin) is present in St. John's wort. Preparations from this plant, used medicinally, contain warnings against exposure to sunlight after consumption. Phototoxins dissolve in alcohol, and for this reason a high-alcohol tincture will be more phototoxic than a St. John's wort tea.

Can plant phototoxicity pose a deadly danger?

- With accidental contact, this is unlikely," says Prof. Adam Matkowski. - The key factors are the amount of phototoxic substances that have penetrated the skin and the duration of sun exposure. The more action of both factors, the more dangerous the effects. Theoretically, one could imagine that someone picked rutabaga, rolled in Sosnowski borscht and still drank a tincture of St. John's wort, and then stayed many hours in the sun. Then there could be a cascading reaction and life-threatening. Such situations, however, are unlikely to happen. On the other hand, it should be remembered that children or sick people with weakened immunity are more susceptible to phototoxicity, and that even in healthy adults, Sosnovskiy hogweed can cause third-degree burns, requiring hospitalization. It is worth being aware of the specific properties of the flora so that communing with nature is a pleasure and does not turn into a nightmare.

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