Welcome to icliniq.com. I could imagine the sufferings of somebody who has a phobia about toxins. It disturbs all the time. The current question is very interesting. It is true that highly lipid soluble chemicals can penetrate the intact skin. If you take bath in water, it will never enter the skin. If you apply oil in the skin, it can enter the skin. This is how, the oil natured (lipid soluble) chemicals can penetrate the skin, but not lipid insoluble (water soluble) drugs. If the skin is having injury opened, then all the chemicals can enter the body. The penetrability through intact skin is based on its lipid solubility, and not based on the size. Even, HIV virus so small, but cannot penetrate the intact skin. It requires an opening in the skin. Poisons like organophosphorus, arsenic, mercury, etc., can enter through the skin. These chemicals are soluble in lipids. Our skin is made by lipid outer layer. The chemical gets into the lipid present in the skin, then slowly enters into it. Thus, higher the lipid solubility, higher the penetration. Even, highest lipid solubility takes much time to enter the skin. Such toxicity happens to people who work in a particular chemical industry. Continuous exposure or contact through the skin for a long period (days, months) leads to the entry of a considerable amount of chemicals. It will not happen simply by touching the chemical for hour. The amount entered within one hour cannot enough to kill a person. If more amount of chemical enters into the body, then it can produce the toxicity to inner organs of our body. As such toxins do not commonly happen to come across in day to day life, you no need to worry about it. The common situation to occur this type is in agriculture field. After using insecticides (contacted with skin), mild amount can enter through skin after applying insecticide to the field, if you take the water bath, you can prevent further entry. I hope this helps to relive your phobia.