Hi. Thank for your query. Since you are a known case of allergic bronchitis for years together, you will have other manifestations too. Te metallic taste n the mouth can be due to the phlegm that comes out of the lower respiratory system. The incidence of coughing spells when you laugh are most probably due to the expectoration coming up the larynx and irritating the vocal cords to instigate the spells of coughing and the excessive coughing irritating the vocal cords more than before. This is a vicious cycle and you have to break this. This is possible by the following: Get a proper clinical evaluation, examination and investigations like X-ray of the chest, tests of blood and stool and so on to get a proper diagnosis and treatment .