The charity said 20 million people are severely short of food and the numbers are rising.
Christian Aid's Head of Humanitarian Programmes for Africa, Maurice Onyango, told Premier South Sudan, Ethiopia, Kenya and Somalia are the hardest-hit countries with people starving to death.
He said: "The recent disappointing rains in Ethiopia, and also in Kenya, have shattered any faint hopes for water sources to fill up, pastures to regenerate and harvests to be viable.
"It has left communities even more reliant on outside aid, stretching humanitarian agencies and local authorities to their limits.
Onyango explained that in Kenya and Ethiopia livestock are dying in their thousands, leaving pastoralist families with no animals, no food, and no assets. He spoke to one famer who lost his entire herd.
He told Premier: "When you see camels dying, it tells you the situation is really grave, because camels are usually quite hardy."
Onyango said people in East Africa have described the drought as the worst the region has had in 30 years.
Last week, the World Food Programme warned that emergency food aid for 7.8 million Ethiopians would run out by the end of June - a claim the government denies.
Onyango told Premier supermarkets are severely rationing food.
Through local partners, Christian Aid is providing safe, clean drinking water to over 21,000 people, distributing food vouchers to 600 families, feeding hundreds of livestock owned by nearly 1,250 pastoralists, and providing support cash to 1,600 families.
Christian Aid launched a fundraising appeal for the East Africa crisis in February 2017.
Onyango encouraged people to support the cause because every little bit helps.
He continued: "I have seen first-hand the difference this makes: it can, and does, save lives."
Click here to listen to Premier's Tola Mbakwe speaking with Christian Aid's Head of Humanitarian Programmes for Africa, Maurice Onyango: