There is this woman who appears in the news every once in a while, named Heidi Falconer. She has such a severe case of hydrophobia (fear of water) that she goes into shock if she drinks a sip of water. When water touches her skin, it burns her. She survives by drinking four small glasses of milk each day and she said that if she receives intravenous saline she goes into shock because the saline is water based. She's had hydrophobia since she was a little girl. Heidi is in her thirties now. What could cause such an extreme phobia?