Philadelphia. His study explained the illness as being due to a combination of cyclic vomiting syndrome, Chagas disease, and Helicobacter pylori. Other possible causes Evidence for familial systemic lactose intolerance syndrome was that vomiting and gastrointestinal symptoms usually appeared two to three hours after meals and that, apparently, Darwin got better when he stopped taking milk or cream. Food intolerance and lactase deficiency may also be confused with food allergies. Symptoms include difficulty swallowing and breathing, nausea, vomiting, diarrhea, and abdominal pain. Upon reaching several other organs in the body, allergens can cause hives, eczema, lightheadedness, weakness, hypotension, etc. This has been proposed as the source of Darwin's illness, but the hypothesis is improbable, because, as with lactose intolerance, its temporal and causal relationship with food is easily established, and this was not always the case. Chronic arsenic poisoning (arsenicosis) has been considered too. This hypothesis has been advanced by John H. Winslow, who published a book arguing that Darwin took arsenic at low dosages as a remedy and that there was "a very close match" between his symptoms and those of arsenicosis. However, it is highly improbable too, due to the long duration of the illness (40 years), the abruptness of symptoms, the cause of his death, and the absence of many symptoms and signs of this kind of poisoning (persistent weight loss and diarrhea, the appearance of dark brown calluses on the palms and the soles of the feet and of skin, known as hyperpigmentation). Barry Marshall proposed in February 2009 that the cause of Darwin's illness was the ulcer-causing bacterium Helicobacter pylori. Marshall, who together with Robin Warren won the Nobel Prize in 2005 for discovery of the bacterium, states that this was a very common gastric infection of the time which causes ulcers in 10% of infected persons and causes dyspepsia in another 10% or so. He had yet to have a short paper on this accepted for publication. Combined causes From a clinical point of view, perhaps Darwin suffered from more than one disease, and had many psychosomatic complications and phobias arising from his debilitating condition. This is known to happen with many patients today, such as in severe cases of panic disorder, usually accompanied by hypochondria and depression. Dr. Peter Medawar has supported the diagnosis that Darwin's health problems were part organic, part psychological. Colp concluded that Darwin's illness consisted most probably of panic