External triggers – What makes psoriasis appear or get worse?
In most cases psoriasis first presents or gets worse as a result of a trigger; something that aggravates the condition. By recognizing your trigger you can maintain an element of control in some ca​ses. Common triggers for psoriasis are: 

1. Skin Injury
Psoriasis can occur for the first time or be triggered by an injury to the skin; this can be the result of a graze or cut or even after injections or sunburn. Repeated minor injuries such as those caused by rubbing or itching can also trigger psoriasis.
2. Viral and Bacterial Infections
Throat infections such as ‘strep throat’ that reoccur in young children and adults can be a trigger for guttate psoriasis. People with affected immune systems; such as HIV patients are more susceptible to psoriasis.
3. Strong Alcohol
Studies have highlighted possible links between alcohol and flare-ups of psoriasis, particularly in men. Alcohol is also known to dry out the skin which can contribute to the severity of symptoms. Alcohol can lead to liver damage which means that medication, processed by the liver, can be less effective. Also, some medications are not suitable for people with liver damage and must be avoided even though they are known to be effective.
4. Smoking
Studies suggest that smoking can play a part in the development of psoriasis. It can increase your risk of psoriasis and can increase the severity of the symptoms.
5. Obesity
Increased skin folds associated with being overweight are a risk factor in all types of psoriasis. Risk of inverse psoriasis is increased if you are obese. Fat cells also produce chemicals that may trigger the condition.
6. Medicine
Certain medications can trigger psoriasis. The most common types of medication to cause a reaction are: 
  • Anti-malarial – taken to prevent infection/spread of malaria 
  • Lithium – taken for depression or psychiatric disorders 
  • ACE Inhibitors - High blood pressure medication 
  • Anti-inflammatory medicine – such as ibuprofen or Indomethacin 
  • Beta blockers – taken by patients with heart failure 
  • Corticosteroids – Prescribed for a variety of health conditions. In this case a sudden discontinuation of relatively high dose can be a trigger.

Please note that psoriasis may only be common to certain brands of the above medications. Always read the information leaflet your medication and discuss any concerns you have with your physician before beginning a course of treatment. Also note, physicians will avoid prescribing medication known to trigger episodes of psoriasis to diagnosed patients, however, in some cases the benefits of taking certain medications outweigh the occurrence of psoriasis.